Englishthelegendsschool.com/cms/DateSheet/75..pdf · Q1) What do the Quran and the traditions of the Prophet (S.A.W) tell us on backbiting and scandal mongering? A) Both the Quran

Legend school of education ,kanitar ,saderbal Class 8th, unit 3

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English

Topic1 : For God's Sake' Hold Thy Tongue

Q1) What do the Quran and the traditions of the Prophet (S.A.W) tell us on backbiting

and scandal mongering?

A) Both the Quran and the traditions of the Prophet (S.A.W) condemn and criticize

backbiting and scandal mongering. The Holy Quran curses such people and the

Hadith compares them to a person eating the flesh of his dead brother.

Q2) What do the Gita and the Bible tell us on backbiting?

A)The Gita says that the freedom from the habit of backbiting is a quality of a person

who is born to God. like endowments. The Bible says that a person, who doesn't

stumble in what he says, is a perfect man.

Q3) What do the Granth Sahib and Lord Budha tell us on backbiting?

A) The Granth Sahib says that the slanderer or the backbiter is always burdened by

the load of his sins. Lord Budha in his eightfold path says that one requires living a

life based on right speech.

Q4) Why did the servant of Rabbi Simeon bring tongue both the times?

a) The servant of Rabbi Simeon brought tongues both the times because he

considered the tongue as a source of both good as well as evil. There was nothing

better than a good tongue and nothing worse than an evil one according to him.

Q5) Why did Rabbi Simeon invite his disciples for a meal?

A) Rabbi Simeon invited his disciples for a meal in order to teach them a valuable

lesson. He served -both the soft and hard tongues at the meal. The disciples ate the

soft ones and left the hard ones untouched. On this Rabbi told them that as they

preferred soft tongues to harder ones for eating, they should always use soft tongue

in conversation too.

Q6) What according to you is the moral of the lesson?

A) The moral of the lesson is that backbiting and scandal mongering are big evils

of our society. We must always refrain from such malice.

Q7) How does our tongue do good or bad to others?

A) When we use our tongue in a soft and polite manner it spreads happiness and

pleasure. But when the same tongue is used in a rude manner it hurts others.

Topic2 : Colours of the Rainbow


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Make sentences with the following words:

Awning: - We could see water droplets falling from the awning.

Barely: - He was so weak that he could barely stand.

Oblivious: - She was so engulfed in talking that she became oblivious to everything

else.

Splendiferous: - The view from the window was splendiferous.

Musings: - She was lost in her own musings.

Convolutions: " Life is filled with convolutions.

Hue : - This painting has many hues.

Tiff: - The friends had a tiff over a small issue.

Brewing: Something is brewing in their minds.

Cherish: - Mother’s nature cherishes enormous lives. .

Q) What did the narrator observe when he looked out?

A) While looking out the narrator observed that the clouds had cleared up after the

rain and sun had also come out. The weather looked very pleasant. He saw drops of

water dripping down the chili plants that had grown just outside the window of his

room. All the attention was centered on the rain drops.

Q) Why was the narrator unable to pay attention to what his daughter was saying?

A) The narrator's mind was totally occupied by the beauties of nature. He was lost

in his own musings. That is why he was unable to pay his attention to what his

daughter was saying.

Q) Why did the narrator have a tiff with his wife?

A) The narrator was lost in his thoughts and could not hear his wife calling him for

tea. This irritated his wife and resulted in a tiff.

Q) What did the narrator find when he returned home late at night?

A) When the narrator returned home, the kids had gone to sleep and his wife was

sitting all by herself As soon as she saw him, she brought him food. Her face was

looking weak which depicted that she had not eaten since morning .Her anger had

disappeared leaving behind only sadness and regret.

Q) Why did the narrator not have appetite?

A) The narrator did not have appetite because he had already had his morning meals

with his friends and spent the afternoon in a cinema hall.


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Topic3: Mercy

Summary

Reference to context:- The quality of 'Mercy' is a famous speech by Portia, in

disguise as a young lawyer, in Shakespeare's play "The Merchant of Venice." She

pleads for mercy from a Jewish money- lender, who holds all the loans and demands

a pound of flesh for the default.

The poem "Mercy" has been written by "William Shakespeare”. He defines different

qualities of mercy by comparing it with power, beauty and godly attributes. The

poet says that mercy cannot be forced on anyone, it is naturally present. It is holy

as if bestowed from the heaven. It is a blessing that not only blesses the one who

takes it but also the one who is giving it. Mercy is displayed to be the most powerful

quality by comparing it with the power of kings. The poet believes that when a king

is merciful, it enhances his beauty more as compared to his crown. Mercy is above

the authority and fear of kings. Although not visible, mercy carries an air of majesty

with it. It resides inside the heart of kings and is a quality bestowed by God itself. In

the last lines, the poet declared that when a decision on earth, is made on the basis

of mercy, it appears like God's decision.

Ql Where does the quality of mercy come from? Who are blessed by it?

A. The quality of mercy descends from the heaven' upon the earth, it blesses both

the persons who give and take mercy.

Q2 How is mercy better than crown of king?

A. Mercy is above the authority and the crown. The poet believes that mercy caries

an air of majesty with it. It's a quality bestowed by God himself

Q3 What does ‘sceptre' stand for? How does it affect the kings?

A. The 'sceptre' stands for the authority of the king. It shows king's power, majesty

and displays the respect and fear of kings.

Q4 When does earthly power look like God's?

A. When justice on earth is done on the basis of mercy, the earthly power looks

like that of God.

Q5 How is mercy alone the ‘sceptred away'?

A. Mercy is above the 'sceptred sway' because it resides inside the heart of kings.

Although not visible, mercy enhances the power and appearance of the king.

Q6 What happens when mercy seasons justice?

A. When mercy seasons justice, it is a display of God's power on earth.


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History

Topic: Civilising the “Native” Educating the Nation.Lesson No. 07Q1: Why did William Jones feel the need to study Indian history, philosophyand law?Ans: William Jones believed that discovery of ancient Indian Texts, understandingtheir meaning translating them and making their findings known to others wouldhelp the British learn from the culture. In order to understand India, Jones believedit was necessary to discover the holy and legal Texts that were produced in ancientperiod. For only those texts could reveal the ideas and laws of country and only anew study of these texts could form the basis of future British policies’ in India.Q2: Why did James Mill and Thomas Macualay think that European educationwas essential in India?Ans: James Mill and Thomas Macaulay regarded oriental learning full of errors.According to them Indian’s should be made familiar with the scientific and technicaladvances that the west had made, so as to teach what was useful and practical andthis they believed this could be done through European Education. Europeaneducation, they declared would, make Indian’s aware of the development in westernscience and philosophy.Q3: Why did Mahatama Gandhi think that English Education had enslavedIndians?Ans: Mahatama Gandhi strongly reacted against western education. He argued thatcolonial education created a sense of inferiority in the minds of Indian’s. It enslavedIndians because it made them to see western civilization as superior and appreciateeverything that came from the west. Westerly educated Indians began admiringBritish rule and they became strangers in their own land. Lastly western educationmade people slaves of machines and technology.Q4: Why did Mahatama Gandhi want to teach children handicrafts?Ans: Mahatama Gandhi strongly argued that education ought to develop a person’smind and soul. He stressed on the method of learning by doing. He believed thatpeople had to work with their hands, learn a craft, and know how different thingsoperated. This would develop their mind and their capacity to understand. Hewanted handicraft to be taught not merely mechanically as is done today butscientifically so that the child should know the why and wherefore of every process.


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Topic: Women, Caste and Reform Lesson No. 08

Q1: What social ideas did the following people support?1. Raja RammohanRao:-Rammohan Rao was a great social reformer who

wanted to reform the Indian society according to the ancient texts. He was infavour of western education and also asked people to read religious texts. Heopposed child marriage, sati and child labour.

2. DayanandSaraswati:He founded the reform organization called AryaSamaj.He wanted to establish a society based on ancient Vedic principles. He raisedhis voice against dowry system caste system, sati and child marriage.

3. VeerasalingamPantulu:-He was a reformer from Madras who dedicated hislife for widow marriage. He supported the upliftment of India women .

4. JyotiRaoPhule: He was a Sanskrit scholar who was seriously critical aboutcaste discrimination in Indian society. He felt that the Hinduism was verydiscriminating towards low caste. He opened schools to impart education tothe low class children in various rural areas.

5. PanditaRamabai: She was an active women reformer who worked toimprove the domestic condition for women. She founded a window’s home toprovide shelter for those women who faced maltreatment by the relatives ofher husband.

6. Periyar:- He criticized the ancient Hindu scriptures and challenged theauthority of Brahmans over low castes. He strongly opposed caste system andgender discrimination.

7. Mumtaz Ali:- She was a Muslim reformer who worked for education towomen. She also supported gender equality.

8. IshwarchandraVidyasagar:- He was strong activist in the field of widowremarriage. By his active efforts he compelled the British government to passwidow Remarriage Act of 1856.

Q3: How did the knowledge of ancient texts help the reformers promote newlaws?

I. The social reformers of India showed by studying ancient texts that manysocial practices had no sanction in the religion.

II. By using the knowledge, they discard the practices and asked people to stoppracticing them.

III. They also suggested the people to study religious texts which make thecommon people inclined towards the reform movements of India.


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Q4: What were the different reasons people had for not sending girls toschool?

i. The people feared that the schools would take girls away from home and thuspreventing from doing domestic work.

ii. The girls had to travel through public places to reach school. The peoplethought that this would have corrupting influence on their minds.

iii. The modern education may be difficult for the parents to marry theirdaughters in the traditional society.

iv. The people also felt that the western education will erode the family andmoral values of their daughters.

Q5: Why were Christian missionaries attack by many people in the country?Would some people have supported them too? If so for what reason?Ans: The Christian missionaries were considered as the destroyers of the religionand culture of Indian people. They had opened educational institutes in villages andtribal areas to propagate their religion. They openly criticized ancient, socialtraditions and customs. They created fear among the people that the Christianmissionaries will convert them.Yes, many people particularly tribal and low castes supported the Christianmissionaries. They thought that it will give them respect and status in the societywhich they were devoid of.Q6: In the British period, what new opportunities opened up for people whocame from castes that were regarded as ‘low’?

i. The poor from villages and towns began to move towards cities when newemployment opportunities were open to them. The planters of northeaststates provided work to the locals of that area.

ii. The army also offered relief to the low castes.iii. A number of Mahar people who were regarded as untouchables found the jobs

in Mahar regiment.iv. In the municipalities of cities and factories demand for labour was increased

as drains had to dug roads to be constructed etc. They went there and workedas labourers.

Q7: How did Jyotirao the reformers justify their criticism of caste inequality insociety?Ans: JyitiRaoPhule was the most influential leader among the low castes. Hedeveloped his own ideas about the injustice of caste society. He sat out to attack theBrahmans who claimed that they were superior to others. Since they were Aryans.He argued that Aryans were outsiders who came from outside of subcontinent andsubjugated the true children of the country. As the Aryans established theirdominance, they began looking at the defeated population as inferiors and low


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castes who had no right to their land and power in reality belonged to thatindigenous people.Q8: Why did Phule dedicate his book Gulamgiri to the American movement tofree slaves?Ans: JyotiRaoPhule dedicated his book Gulamgiri to the American movement to freeslaves in order to establish a link between the American slaves and their movementand the low castes of India. He thought that this will encourage the low castes tofight against this oppression.Q9: What did Ambedakar want to achieve thought the temple entrymovement?Ans: Dr. Ambedakar started temple entry movement in 1927 which was particularlyby the people belonging to Mahar caste. The lower caste people including Dalitsstarted to use water from temple tanks which outraged the Brahmans. His aim wasto show the power of caste prejudices within the society.Q10: Why were JyotiPhule and Rama Swami Naicker critical of nationalmovement? Did the criticism help the national struggle in any way?Ans: JyotiRaoPhule and Rama Swami were critical of the nationalist movementbecause they thought that the national leaders do not pay attention to the light oflow castes. Their criticism compelled the leaders to take the cause of lower castewhich helped the nationalist movement by popular support.


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Geography

Topic5: Industries

i) What is meant by the term 'Industry'?

Ans: The term "industry' refers to an economic activity that is concerned with

production of goods, extraction of minerals or the provision of services. For example;

steel industry for production of goods, coal mining industry for extraction of coal &

tourism industry as service provider.

ii) Which are the main factors which influence the location of an industry?

Ans: The main factors that influence the location of an industry are as follows:

a) Availability of raw material.

b) Availability of labour.

c) Proximity to markets.

d) Transport facilities.

e) Power supply.

f) Capital investment and

g) Availability of land & water.

h) Sufficient and efficient technical know how.

iii) Which industry is often referred to as the backbone of modern industry & why?

Ans: Iron & steel industry is known as the backbone of modern industry. It is because of

the following reasons:

i) Iron and steel industry acts as a feeding spoon for each and every industry

either directly or indirectly. As its furnished products are used as raw material

in other industries and it is the basic and ultimate industry which uses machines and

creates other machinery which are henceforth used in different sectors,


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ii) Machines & equipments are all made of steel e.g. Farm machines are mostly of

steel, oil wells are drilled with steel machinery, steel pipelines transport oil, minerals

are mined with steel equipment.

iii) The transport sources like trains, ships, trucks and autos are all made of steel.

iv) Why cotton textile industry rapidly expanded in Mumbai?

Ans: The cotton textile industry rapidly expanded in Mumbai because of the

following reasons:

1. Availability of raw cotton.

2. Availability of market.

3. Transport facilities including accessible port facilities.

4. Availability of cheap & skilled labour and

5. Favourite warm and moist climate.

Q3) Distinguish between:

i)Agro based & Mineral based Industry.

Agro-based Industry Mineral based IndustryThe Agro-based industry use plant& animal products as rawmaterials.

Mineral based industries usemineral ores as their raw material.

These industries have no largeinvestment.

These industries have a largeinvestment.

These industries are a source ofemployment for people in ruralareas.

These industries are a source ofemployment for people in rural aswell as urban areas.

Agro-based industries are cotton,silk, jute, woolen textile, edible oil,dairy products & leatherindustries.

Mineral-based industries are iron &steel industry, Aluminumsmelting,•\cement industry etc.

THE LEGENDS SCHOOL OF EDUCATION CLASS 8TH Unit 3

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CIVICSTopic7: Understanding marginalization

Q1 . Write in your own words two or more sentences of what you understandby the word marginalisation?Ans . Marginalisation can be defined as the process whereby something orsomeone is pushed to the edge of a group and accorded lesser importance. Itis predominantly a social phenomenon by which a minority or sub group isexcluded and their needs or desires are ignored. Depressed classes are alsoknown as marginalized section of society.Q2 . List two reasons why Adivasis are becoming increasingly marginalized?Ans . The two reasons for Adivasis to become increasingly marginalized are:1. People think they lack advancement as they are resistant to new ideas.2. As they are used to living in forests their migration to urban areas createsproblem for them and they are not able to adjust to urban life.Q3 . Write one reason why do you think the constitution safeguards to protectminority communities are very important?Ans . The safeguards to protect minority communities are necessary, becausethe majority community may culturally dominate the minority communityand the minority community might become marginalized.

Public –Sector Industry Joint-Sector Industry

The public-Sector industries are owned

& managed by the central or state

governments or by their agencies.

The Joint-Sector industries areowned & managed jointly by theprivate firms & the governmentagencies.

Bhilai Steel Plant, Bharat Heavy

Electricals Hindustan Aeronautics &

steel Authority of Indian are examples

of public sector industries.

Maruti Udyog limited, PunjabNational Bank & Oil India are JointSector Industries.


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Q4 . Re - read the section on minority and marginalisation. What do youunderstand by the term minority?Ans . Minority is the community that is numerically small in relation to therest of the population. A particular religious section which has a lowpercentage in population compared to the major religious community is calleda minority.The constitution of India provides safeguards to linguistical and religiousminorities, as a part of its fundamental rights and ensures that minorities donot face any disadvantage or discrimination. In India, Christians, Sikhs,muslims , etc. are included as a minority.Q5. You are participating in a debate where you have to provide reasons tosupport the following statement: 'Muslims are a marginalized community '.Using the data provided in this chapter list two reasons that you would give.Ans. As per the data provided in the chapter, the literacy rate of Muslimpopulation in India is only 59% which is the lowest compared to 65% amongHindus 70% among Sikhs 73% among Buddhists 80% among Christians and94% among jains. Also, only 3% of muslims represent the esteemed Indianadministration service cadre.Q6 . Imagine that you are watching the republic day parade on TV with afriend and she remarks, " look at these tribal people they look so exotic andthey seem to be dancing all the time. " List three things that would tell herabout the lives of Adivasis in India.Ans. Adivasis have a deep knowledge of forests. They are hunters andgatherers and lived like nomads. They practiced shifting agriculture and havealso cultivated at the single place. Their deep knowledge of forests made themindispensable to the rules of various empires during the pre colonial period inIndia. They have their own knowledge and have influenced the formation ofvarious Indian languages. Bengali being one of them.Q7 . In the story board you read about how helen hopes to make a movie onthe Adivasis story. Can u help her by developing a short story on Adivasis ?Ans. Gonds, birhor ,santhala, Mundas, orans etc. are some tribes. Gonds is ameasure tribe of M.P. bihar and orissa .Gobindha maran was displayed due toa refinery project in orissa. He is having the daughter and two sons. He isliving a miserable life. His daughter developed relation with a boy of highercaste which was not liked by Mr.Maran. Due to family clash both boy and girlcommitted suicide.

Q8 . Would you agree with the statement that economic marginalisation andsocial marginalisation are interlinked? Why?


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Ans. Social marginalisation and economic marginalisation are interlinked.Social marginalisation forces a social group out of the mainstream, resulting inlack of opportunities for skill development and education. This means that thepeople from marginalized section will not have proper access to qualityhealthcare, which in turn means that a child from a marginalized section doesnot develop into a financially stable adult, who otherwise is capable enough toensure a better income. Thus, the individual who is left behind insocioeconomic development, also becomes economically marginalized.

Chapter.2 of u3

Topic 8 : Confronting marginalisationQ1. List two fundamental rights in the constitution that dalits can draw uponto insist that they are treated with the dignity and as equals ?Ans. The fundamental rights of the constitution which dalits can draw upon tobe treated with dignity and as equals are:Right to equality: All persons are equal before the law. No citizen can bediscriminated against on the basis of his or her socioeconomic background,caste, religion etc.Right against exploitation: The constitution prohibits trafficking, forcedlabour and work performed by children under 14 years of age. One cannot beexploited or forced to do any particular job because of one's poor resourcesetc.Q2. Re read the story on Rathnam as well as the provisions of the 1989 SC andST prevention of atrocities Act .Now list one reason why do you think he usedthis law to file a complaint.Ans. Rathnam used the law because he refused to perform the sadistic ritual,the powerful castes in the village decided to teach him a lesson. They orderedthe community to ostracise him and his family, and everyone was told that noone should speak or do any work for them or with them. Some men evenburnt his house down and tried to burnt him and his family alive.Q3. Why do Adivasi activists, including c.k.janu ,believe that Adivasis can alsouse this 1989 Act to fight against dispossession? Is there anything specific inthe provisions of the Act that allows her to believe this?Ans. Adivasi activist including c.k.janu, believe that Adivasis can also use the1989 Act to fight against dispossession because this act guarantees the tribalsnot to be dispossessed from the land resources forcibly. They pointedspecifically that this act merely confirms what has already been promised tothe tribal people in the constitution that their land cannot be sold to orbrought by non tribal people. The constitution also guarantees the right of thetribal people to repossess their land.


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Chemistry

Topic: Combustion and Flame1. List the conditions under which combustion can take place.

a. There are three essential conditions for combustion to take place:i. Presence of a combustible substance.

ii. Presence of supporter of combustion i.e. oxygen.iii. Attainment of ignition temperature.

2. Fill in the blanks: Do it yourself3. Explain how the use of CNG in automobiles has reduced pollution in our

cities?a. CNG is cheap, readily available and highly combustible. It

has a high calorific value. The use of CNG in automobiles has reducedpollution in our cities because it produces the harmful products in verysmall amount and it is a cleaner fuel as it does not produce harmfulgases and does not leave any residue after burning.

4. 'Compare LPG and wood as fuels.a. Following are the differences between wood and L.P.G:

LPG WoodIt doesn't leave any residue afterburning.

It leaves behind lot of ash afterburning.

It can be transported throughpipelines and cylinders.

It cannot be transported easily likeLPG.

It burns easily. It catches fire with difficulty.It has low ignition temperature. It has high ignition temperature.It doesn't produce smoke on burning. It burns with smoke.

5. Give reason:a. Water is not used to control fires involving electrical equipment.

i. Water is not used to control fires involving electricalequipments because water is a good conductor of electricityand can result in an electric shock to a person in contactwith water.

b. LPG is a better domestic fuel than wood.i. LPG is a better domestic fuel than wood because it neither

produces gases nor leaves residue that pollute theenvironment. Besides, LPG has high calorific value thanwood.


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c. Paper by itself catches fire easily whereas a piece of paper wrappedaround an aluminium pipe doesn't.

i. Paper by itself catches fire easily because its ignitiontemperature is low, while a piece of paper wrapped aroundan aluminium pipe doesn't catch fire because its ignitiontemperature is high.

6. Name the unit in which calorific value of a fuel is expressed.a. The unit in which calorific value of a fuel is expressed is kilojoules

per kilogram (KJ/Kg).7. Explain how CO2 is able to control fires.

a. C02 being heavier than oxygen, covers the fire like a blanket andalso brings down the temperature of combustible substance. Sincethe contact between the combustible substance and oxygen is cutoff, the fire is controlled.

8. It is difficult to burn a heap of green leaves but dry leaves catch fire easily.Why?

a. It is difficult to burn a heap of green leaves because its ignitiontemperature is high, but dry leaves catch fire easily as theirignition temperature drops or becomes low.

9. Which zone of a flame does a goldsmith use for melting gold and silverand why?

a. A goldsmith uses the outermost zone of a flame for melting goldand silver because it is the hottest zone of the flame (temperature= 800 C).

10.In an experiment 4.5kg of a fuel was completely burnt. The heat producedwas measured to be 1,80,000KJ. Calculate the calorific value of the fuel.

Ans. Calorific value = KJ/Kg.1,80,OOOKJ = 40,OOOKJ/Kg.4.5kg

11.Can the process of rusting be called combustion? Discuss.a. The process of rusting can be called as combustion because iron is

oxidized and energy is released but this happens so slowly thatwe cannot see it happening.

12. Abida and Ramesh were doing an experiment in which water was to beheated in a beaker. Abida kept the beaker near the wick in the yellow partof the candle flame. Ramesh kept the beaker in the outermost part of aflame. Whose water will get heated in a shorter time?

a. Ramesh's water will get heated in shorter time.


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Additional Questions1. Define the following:-

a. Combustion:- The process of burning of a substance in presence ofoxygen with the evolution of heat and light, is called combustione.g. when a magnesium ribbon is heated, it combines with oxygento form magnesium oxide along with a liberation of heat and light

Mg + O2 MgO + Heat + Lightb. Combustible substance:- The substances that can react with

oxygen and give off heat and light, are called combustiblesubstances e.g. wood, paper, kerosene etc.

c. Inflammable substance:- The substances which have very lowignition temperature and can easily catch fire with a flame, arecalled inflammable substances.

d. Ignition temperature (Kindling temperature):- The minimumtemperature, to which a substance must be heated in order tocatch fire, is called ignition temperature.

e. Calorific value of fuel:- The amount of heat energy liberated byburning 1kg of fuel completely in oxygen is called calorific value ofa fuel. Calorific value of the fuels is expressed in kilojoules per kge.g. C.V of coal is 25,000-33,000 kj/kg.

f. Flame:- It is a zone of combustion of gaseous substances with theevolution of heat and light.

g. Fuel:- A fuel is a material that is burnt to produce heat and otherforms of energy.

2. What are the different types of combustion?a. According to speed of combustion, it is of following types:

i. Rapid combustion:- It is a type of combustion in which largeamount of heat and light are produced in short period oftime. E.g. burning of gas in a burner or kerosene in a stove.

ii. Slow combustion:- It is a type of combustion which takesplace slowly and at a lower temperature e.g. Rusting of iron,oxidation of food in our body.

iii. Spontaneous combustion:- It is a type of combustion inwhich substance catches fire as soon as it is exposed to aire.g. burning of white phosphorous.

iv. Explosion:- A reaction involving release of tremendousamount of heat, light and sound in a very short interval oftime is called explosion e.g. burning of a fire cracker,combustion of hydrogen.


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Depending upon the availability of oxygen, it is classified as:a. Complete combustion:- When a substance burns in sufficient supply of

oxygen, it burns completely producing large amount heat and light. It iscalled as complete combustion.

b. Incomplete combustion:-When a substance burns in limited supply ofoxygen, it burns incompletely producing carbon monoxide, water andless amount of heat. It also produces soot which contains unburntcarbon particles.

3. What are the conditions necessary for combustion to take place?a. There are three conditions which are necessary for combustion to

take place. These are:-i. Presence of combustible substance:- The presence of

combustible substance is necessary for combustion to takeplace. A combustible substance is actually the food for fire.

ii. Presence of supporter of combustion:- Substances only burnin sufficient supply of air i.e. oxygen. If the supply of air ishindered the substance will not burn.

iii. Heating the combustible substance to its ignitiontemperature:- Before combustible substance can catch fireand burn, it must be heated to a certain minimumtemperature by supplying heat from outside. The lowesttemperature at which a substance catches fire and startsburning is called its ignition temperature.

4. What is a fire extinguisher and what are the different types of fireextinguishers?a. A fire extinguisher is a device that is used to extinguish fire by the

release of C02. A fire extinguisher extinguishes fire by applyingfollowing principles:-

i. By lowering temperatureii. By cutting supply of oxygen

iii. By removing the combustible substanceThere are three types of fire extinguishers that are commonly used:

1) Dry powder fire extinguisher:- It contains sand and baking soda(NaHCO3). When this mixture is thrown over fire, baking sodadecomposes to release carbon-dioxide which extinguishes the fire.

2NaHCO3 Na2C03 + CO2 + H2O(Baking soda)(Sodium bicarbonate) (Sodium carbonate)


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2) Soda acid type fire extinguisher:- It consists of small glass bottle filledwith sulphuric acid that is supported in a strong iron vessel containingsodium bicarbonate solution. On striking the knob, the acid bottlebreaks and carbon dioxide is released.

3) Foam type fire extinguisher:- In this type, a solution of aluminiumsulphate is taken in glass bottle, instead of sulphuric acid. It gives offfoam of carbon dioxide that surrounds the burning substance and cutsoff its air supply. This type of fire extinguisher is specially used toextinguish oil fires.

(A12(SO4)2 + 6NaHCO3 2Al(OH) 3 + 3Na2SO4 + 6CO2

4) Carbon tetrachloride fire extinguisher:- In this extinguisher, carbontetra chloride is pumped out from the cylinder and it vapourises andthus extinguishes the fire by inhibiting the combustion process. Thevapours of carbon tetrachloride being heavier than air settles oncombustible substance and covers its surface and thus cuts its contactwith oxygen.

SODA ACID FIRE EXTINGUISHER5) Define fuel. What are the characteristics of an ideal fuel?

a. A fuel is a substance that is used to produce heat or energy byburning. The characteristics of an ideal fuel are:-

i. It should be cheap and readily available.ii. It should have high calorific value.

iii. It should be easy to store, handle and transport.iv. It shouldn't produce toxic fumes or smoke.v. It should not leave behind excess of ash.

vi. It should have convenient ignition temperature.6) Write a detailed note on the different types of fuel.

a. On the basis of state, fuels are classified as solid, liquid and


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gaseous fuelsi. Solid fuels:-These are the fuels which occur in solid state.

Coal, wood, coke etc. Solid fuels require much space forstorage, give out smoke and leave ash on burning.

ii. Liquid fuels:- These are the fuels which occur in liquid statee.g. petrol, kerosene, diesel etc. They leave no residue whenburnt and can be stored easily.

iii. Gaseous fuels:- They are fuels which occur in gaseous statee.g. natural gas, petroleum gas, water gas etc. They havehigh calorific value, leave no residue when burnt, don'tcause pollution and have low ignition temperatures.However, they are difficult to store and transport.

On the basis of occurrence fuels are classified as :• Natural fuels:- These are also called as a primary fuels. These are the fuelsthat exist in nature and are used in the same form e.g. coal, wood, cow dung.• Processed fuels:- These are also called secondary fuels. These are the fuelsthat are produced from natural fuels after processing by chemical methodse.g. petrol, diesel, biogas etc.

7) Define flame. What are the different parts of a candle flame?a. It is a zone of combustion of gaseous substances accompanied by

evolution of heat and light. Only that substance which burn andvapourise produces flame. The combustible substance and thesupporter of combustion should be both in gaseous state in orderto produce flame. A flame is the visible light emitting gaseouspart of fire. It is a highly exothermic reaction. The different partsof a candle flame are:-

i. Zone of non-combustion (Dark zone):- This is the dark zonethat lies around the wick. It contains unburnt gas particles.No combustion takes place here as no oxygen is available.

ii. Zone of incomplete combustion (Luminous zone):- In thiszone, the hydrocarbons present in wax decompose intocarbon and hydrogen. The unburnt carbon particles imparta yellow colour to the flame.

iii. Zone of complete combustion (Non -luminous zone):- It isthe outermost hottest region in the flame that is invisible.Here, carbon and hydrogen are completely oxidized tocarbon dioxide and water vapour.

iv. Blue zone:- It lies at the bottom of the flame. The blue colour


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is due to the burning of carbon monoxide produced due tothe incomplete combustion of carbon particles.

8) Write a detail note on :-Pollution caused by burning of carbon fuels:- Burning of fuels containingcarbon also cause serious health problems. When the fuel is burnt, the un-burnt particles of carbon remains suspended in the atmosphere, and causesrespiratory problems. Asthma is respiratory disease that has become commonthese days. Sometimes incomplete combustion takes place due to limitedsupply of 02 resulting in the formation of CO (carbon monoxide) which mayeven prove to be fatal. Sulphur and nitrogen oxides released during thecombustion of fuels dissolve in rain water and cause acid rain. Acid rain is avery harmful for crops, buildings and soil. The decoloration of Taj Mahal overthe years is because of acid rain. Carbon dioxide is released when fuel is burntwhich leads to global warming. Global warming is the rise in temperature ofatmosphere of the earth. These result, in the melting of polar glaciers, whichleads to a rise in sea level, causing floods in the coastal areas. Low lyingcoastal areas may even be permanently sub merged under water.Flame:- A flame is a zone where the burning of gases or vapour takes placewith the production of light i.e. A flame results due to the rapid combustion offuel.The fuels burn with a blue flame, when there is sufficient supply of air. Butwhen the supply of air is inadequate, colour of the flame is yellow. Only thosesolid and liquid substances which vaporize on heating burn with a flame,when a fuel burns completely, a flame without smoke is obtained. If the fuel isnot completely burnt, smoking flame is obtained. The smoke contains unburntcarbon particles (soot)Q) How does a candle burn?a) A candle is made of paraffin wax that contain hydrocarbons. When theyare heated, the hydrocarbons melt. The liquid hydrocarbons are converted tovapour which catch fire and produce a flame. Flame of candle has threedifferent zones:-

Zones of Flame (Zones of candle flame):1. The Innermost Zone (Dark Zone):- The inner most zone of the flame is

cooler than other zones and it is dark. It contains the fuel (wax) in


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the gaseous state. In this zone, no oxygen is available for the burningto take place. If we place one end of a glass tube in the dark zone andhold a burning matchstick near the other end, the vapours of unburntfuel coming out at the other end will burn.

2. The Middle Zone:- This is the largest zone of the flame. It is also calledas luminous zone. It is brightest zone. In this zone, the fuel burnspartially and forms carbon particles. The hot carbon particles emitlight. This zone gives soot and smoke.

3. The Outermost Zone or Non luminous zone:- This zone of the flame isthin and blue in colour. As the oxygen from the air is readilyavailable in this zone, there is complete combustion of the fuel. Thisis the hottest zone of the flame. The temperature in this zone ismaximum around 1800°C.

Global Warming:- It is the heating up of earth due to the rise in temperature. Ithappens when green house gases (C02, Water vapour, Methane) trap heat andlight from the sun in the earths atmosphere, which increases the temperature.The heat and light can get through the atmosphere, but it can't get out. As aresult, the temperature rises. This phenomenon is termed as green houseeffect.The atmosphere covers earth's surface it allows solar radiations to passthrough it to strike the earth surface. However, it presents the infra redradiation to reflect back from earth and to escape into space. Gases like CO2,methane are called green house gases. Out of these CO2 is the most important.They help to keep the earth warm. The mean average temperature of the earthis around 15°C. In the absence of green house gases, it may drop to -26°Ckilling all the life on earth.Man is adding large amount of CO2 and CH4 to the atmosphere by burning offossil fuels in homes, industries. Also deforestation increases CO2 inatmosphere as there are no trees to utilize this C02. So, the concentration ofgreen house gases increases and more and more heating of earth's surfacetakes place. This is known as Global Warming.Effects of Global Warming:1. It causes an increase in the sea level due to melting of glaciers, polar ice.2. It causes climatic changes in environment.3. It changes precipitation patterns.


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Biology

Topic: Food Production & ManagementAgriculture: It is derived from two Latin words Ager-land, Cultura- cultivationso agriculture means cultivation of crops. The branch of science thatdeals with the growth of plants and animals for human use is calledagriculture.Agriculture includes four main processes:i) Cultivation of soil which is called as soil management.ii) Growing and harvesting of crops which is called crop farming.iii) Growing and harvesting of vegetables, fruits, flowers and decorativeplants which is called Horticulture:iv) Breeding and raising of livestock including poultry called animalhusbandry.Crop plants or crops:The plants of same kind grown and tended in a field onlarge scale to obtain foods like cereals, pulses, vegetables, fruits etc. is calledcrop. These are of three types :Cash crops: These are those crops that are cultivated for commercial purposese.g. coffee.Catch crops: These are those crops that are grown in between two main cropse.g. radish, carrot, peas, etc.Cover crops:- These are the crops which are grown in order to maintain thefertility of the soil e.g. leguminous plants.Depending upon the crops there are two main seasons:

1) Rabi season 2) Kharif seasonThe crops grown in Kharif season are called Kharif crops and the crops grownin rabi season are called Rabi crops.Kharif crops:- These are those crops that are sown at the beginning of themonsoons i.e.in the month of June and July and harvesting is done inSeptember and October after the monsoon rains are over. They require lot ofwater e.g. rice, maize, cotton, ground nut etc.Rabi crops:- These are those crops that .are grown between October andDecember i.e. in the beginning of winters and are harvested after winter inMarch or April. These do not require a lot of water e.g. wheat, barley, gram,mustard, potato, etc.Methods of agriculture/ Basic practices of crop production:- The various tasks


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performed by a farmer to produce a good crop are called agriculturalpractices. The various agricultural practices are:-1) Preparation of soila) Ploughing b) Levelling c)Adding manures and fertilizers2)Sowing3)Adding manures and fertilizers4) Irrigation5) Weeding -6)Protection of crops from pests and other organisms.7) Harvesting, threshing and winnowing.8) StoragePreparation of soil: The soil is prepared for sowing the seeds of the crops byPloughingLevelingManuring

1) Ploughing (digging or tilling):-The process of loosening and turning the soil with the help ofploughs, is called ploughing. The implements that we use for smallareas are spade, shovels, hoe, etc. ploughing pulled by a pairs ofbullocks and tractors are used for large areas.

Functions of ploughing:1. It looses up the soil for proper aeration and allows the roots to breathe

easily.2. It allows the plant roots to penetrate deeper into the soil.3. Loose soil mixes fertilizers uniformly.4. It brings the nutrient rich soil to the top so that the plants can use these

nutrients.5. It helps in the growth of soil organisms such as earth

worms, millipedes, bacteria and fungi.6. It helps in uprooting the weeds.7. It exposes the soil pests to natural predators.

Q) Why are earth worms called as farmer's friend'?a) Earth worms are called as "farmer's friends'' because they ensureaeration of the soil. Their waste and the decay of dead organisms also help inmanuring the soil.Levelling:- The process of making the soil surface uniform is called levelling. Inthis process, big pieces of soil called crumbs are broken down into smallerpieces for proper germination. It is done by making use of a wooden plank oran iron leveller.


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Advantages ofleveling:1. It breaks the crumbs into smaller pieces for proper germination.2. It protects the upper fertile layer from erosion.

3. It provides uniform irrigation.Manuring:- Manuring means adding manures to the soil. Manure containsmany nutrients required for the growth of crop plant. So, manuring is done toincrease the fertility of the soil before seeds are sown into it.Once the soil is ploughed, levelled and manured, it is ready for sowing ofseeds. The soil is watered before sowing.Sowing:- The process of putting or scattering the seeds into thesoil for growing the crop plants is called sowing.Quality of seeds:

1. The seeds that are chosen should be of good quality.2. They should be healthy.3. They should be disease resistant.4. They should be free-from diseases.5. They should -be high yielding.

Precautions for sowing seeds:1. Seeds should be placed at a correct depth.2. Seeds should be planted at a right distance.3. Soil should have enough water.

Methods of sowing:There are three methods of sowing:

1. Broadcasting2. Seed Drill3. Transplantation1) Broadcasting:- It is a traditional method of sowing the seeds

in which seeds are sown manually by hand.Disadvantages of broadcasting:

v. It does not ensure proper spacing or proper depth of the seeds.vi. The seeds scattered on the surface of the soil for sowing can be

picked up and eaten by the birds easily.2) Seed Drill:- It is along iron tube having a funnel shaped opening leading

to long tubes. It is tied to the back of a plough and seeds are put into thefunnel. The drill deposits seeds at regular interval which ensures moreaccurate sowing of seeds.

Advantages of sowing with a seed drill:1. Seeds are sown at correct depth and correct intervals. The seeds sown

are in regular rows.


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2. The seeds get covered by soil and hence these seeds cannotbe picked up and eaten by birds.

3. Sowing by using a seed drill saves time and labour.3) Transplantation:- The process of transferring the seedlings from the

nurseries or seeds beds to the main field.Advantages of Transplantation:

1. It helps the farmers to select the healthy seedlings and space themproperly while planting. This results in increase in crop yield.

2. It allows better penetration of the roots in the soil. It promotes betterdevelopment of the shoot system of plants.

Applying manures and fertilizers: The deficiency of plant nutrients and organicmatter in the soil is made up by adding manures and fertilizers to the soil.Manures:- We add the manures and fertilizers in order to replenish nutrients.These are the organic substances obtained by the decomposition of plants,animals and their waste which supplies essential elements and humus to thesoil and makes it more fertile. These are formed of three elements i.e. carbon,hydrogen and oxygen. Carbon is present in large amount. There are threetypes of manures:Farm yard manures:- Those manures which we get after decomposition ofanimal dung or leaves or straw are called farm yard manures.Compost manures:- These are those manures which we get afterdecomposition of dead plants, clay, dead animals, urine of animals, mud etc.These are kept in layers for 5-6 months and then compost manures areobtained.Green manure:- These are those manures which are obtained by thedecomposition of leguminous plants e.g. peas, beans etc.Advantages of manuring:

1. It enriches the soil with nutrients.2. It adds organic matter to the soil which improves the quality of the soil.3. It increases the water holding capacity of the soil.4. It increases the population of useful micro-organism.5. It improves and maintains the quality of the soil.

Fertilizers: A fertilizer is a manmade inorganic compound which suppliesspecific nutrients to the soil. It is a salt or an organic compound containing thenecessary plant nutrients to make the soil more fertile. The most commonlyused fertilizers are NPK (Nitrogen, phosphorous, potassium) fertilizers.Fertilizers have been very popular with farmers because most of them arewater soluble and can be absorbed by the plants easily. These are also veryeasy to handle and store.


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Fertilizers are applied either by broadcasting or by spraying or throughirrigation channels.Examples are: Ammonium sulphate, super phosphate, potassium nitrate, ureaetc.Manures FertilizersManures are organic in nature. Fertilizers are inorganic in nature.They are rich in organicnutrients but not rich in NPK.

They are rich in NPK.

They restore the texture of soilfor better retention of water.

They cannot do this.

They are voluminous and so difficultto store and transport.

They are in concentrated formand are easy to transport but properprecautions should be taken whilestoring.

They are not soluble in waterand so are absorbed very slowly byplants.

It readily dissolves in water andis quickly absorbed.

They are not nutrient specific. They are nutrient specific andso can be selected to restoredeficiency of specific nutrients in thesoil.

Excessive use does not harm the soiltexture. They provide humus to thesoil.

Excessive use can change thechemical composition of the soil andhence pollute water.

Disadvantages of excessive use of fertilizers:IV. The excessive use of fertilizers changes the chemical nature of soil and

makes the soil less fertile.V. The excessive use of fertilizers causes water pollution in ponds, lakes

and rivers etc.VI. The application of too much fertilizers result in the leeching of nitrates

and phosphates into rivers, lakes etc. Phosphates and nitrates cause"Eutrophication".

Eutrophication:- It is the condition where the nitrate sand phosphatesincrease the growth of algae to produce algal bloom. This uses up oxygen andencourages aerobic bacterial growth and thus kills other aquatic animals.Nitrates in the ground water find their way into drinking water. Thesecompounds are cancer causing. Nitrates oxide the iron in haemoglobin andthus haemoglobin is no longer able to combine with Oxygen which leads to the


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oxygen deficiency in the body. The extreme form of nitrate poisoning is "Blue-baby-syndrome" in which the body turns blue due to the lack of oxygen.Irrigation: The process of supplying water to crop plants in the fields is calledirrigation.Advantages of irrigation:

i. Irrigation before ploughing the fields makes the soil soft due to whichploughing of fields becomes easier.

ii. It is necessary to' provide moisture for the germinations of seeds.iii. It is necessary to maintain the moisture of soil for healthy crop growth

so as to get good yield. It is necessary for the absorption of nutrients bythe plants from the soil.

Sources of irrigation:- We can irrigate our fields in two different ways:-I) Traditional methodsII) Modern methods

Traditional methods:- These are the primitive and ancient methods. Irrigationfacilities are not well developed. The various traditional methods of irrigationare:-a) Moat (Pulley system)b) Chain pump.

c) Dhekli andd) Rahat (Lever system).

Modern methods:- These are the methods in which advanced technology isused. Irrigation facilities are well developed. The modern methods ofirrigation help us to use water economically by preventing its wastage. Thereare four types methods of modern irrigation1) Furrow irrigation 2) Basin irrigation3) Sprinkler irrigation 4) Drip irrigation1) Furrow irrigation:- In this type of irrigation furrow or channels are madein between the crop rows and water is put in them. Since all the channels areinterconnected, water reaches to every crop.2) Basin irrigation:- In this method water is kept in fields as suchso that the crops get sufficient water.3) Sprinkler irrigation: In this method of irrigation fountain or sprinklers areused at particular distances for watering the plants.4) Drip/Trickle/Micro-irrigation:- In this method, a pipe is connected to awater reservoir and various small channels are taken out from the pipe insuch a way that their ends reach the bases of the crop (so for 1 crop there is 1end) and valves are fixed at specific intervals. When the crops need to beirrigated, these valves are opened and water thus reaches to the crops.Advantages of drip irrigation

I) It prevents wastage of water.


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II) It prevents water logging.III) It minimizes the use of water in agriculture. So, drip irrigation is very

useful in those areas where the availability of water is poor.IV) The time and frequency of irrigation depends on types of soils, crops

and seasons or we can say that it varies from soil-to-soil, crop-to-crop and season-to-season.

Crop to crop:- Rice fields need stagnant water before sowing till harvestingwhile maize needs less water.Soil to soil:- Clayey soil can retain water while as in sandy soil water seepsdown to fit bottom and thus crops can't grow in it.Season-to-season:- In summer season, plants need to be watered twice a day asthe water evaporates quickly whereas in winter, plants, get water naturallyfrom rains and snow.Disadvantages of excessive/untimely irrigation:Excess of water i.e. water logging inhabits the process of germination of seedsas the seeds do not get sufficient air to respire.

I) If the crop is irrigated when fully mature, it gets damaged.II) It leads to wastage of water.III) It turns the field into marshy area.IV) Due to water logging flowers wither and fruits become rotten.

Weeding: The process of removal of weeds is called weeding.Weeds:- The unwanted plants that grow along with the main crop (of theirown) are called weeds. The weeds compete with the crops i.e. they competewith the nutrients, food, water, sunlight, air etc supplied to the crops.Examples of weeds:

I) PartheniumII) AmaranthusIII) ChenopodiumIV) WildoatsV) Grass

The best time for the removal of weeds is before they produce flowers andseeds. We remove the weeds either by pulling them out or with using a trowel(Khurpa) or by destroying the weeds by spaying special chemicals calledweedicides.Weedicides:- The poisonous chemicals which destroy the weeds only withoutharming maincrop.The another name of weedicides is herbicides.Examples of Weedicides:

I) DalaponII) Siniazine


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III) PicloramIV) 2,4-DV) Butachlor

Steps to take while using weedicides9. The person spraying the weedicides must cover his nose and mouth

because if the vapour of weedicides enter the body of a person they maylead to the death of the person. They are toxic in nature.

10. We should wash the obtained grains thoroughly beforeconsuming so that if any weedicide is left, it will be washed off.

Protection of Crops: Crops are to be protected from pests by sprayingpesticides.Pests:These are the organisms that destroy our crops are called pests.Pesticides:- The chemicals that are used to destroy pests.Examples of Pests:- Rodents (rats), insects (weevil, locusts terminates) microorganisms.

1. It is observed that 10% of our crop yield is destroyed by pests.2. The 80% of sugarcane cultivation is destroyed by locusts.3. Termites enter the plants and make them hollow.

Micro-organisms: They also destroy our plants e.g. Smut is a disease causedby fungi wheat, wilt, is caused by bacteria etc.There are two methods to remove the pests:

1. Chemical control2. Biological control

Chemical control: We spray the chemicals on the ground or to the field. It canbe done by:1) Hand operating machine 2) Low lying air crafts.In chemical control we use pesticides which include:-Insecticides:- They kill insects e.g. DDT (Dichlorodiphenyl Trichloroethane),BHC (Benzene hexachloride) Commonly called gamaxene, Malathion etc.Fungicides:- Chemicals that are used to destroy fungi e.g. sulphur and coppersalts.Rodenticides:- The chemicals that are used to kill rodents are calledrodenticides e.g. Zinc phosphide, Warfarin.Biological control: In biological control, we make use of another organismwhich kills the pests.Advantages and Disadvantages of using pesticides:Advantages:

1. They kill pests quickly.2. These increase food production by killing pests.


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3. They are easy to store and use.Disadvantages:

1. Pests can develop resistance to a particular pesticide.2. The spray can effect wildlife when sprayed in a particular area.3. Pesticides can seep into the soil and drain into rivers and lakes and

pollute the water.4. They can enter the food chain and build up from one feeding level to

another feeding level and can reach a toxic level. Being toxic, theyirritate the skin and effect the respiratory system of human being.

Harvesting, Threshing and Winnowing:-Harvesting:It is the process of cutting and gathering of mature crops. In harvesting, thecrops cut close to the ground by hand using a cutting tool called sickle. This iscalled manual harvesting. It is done in small areas. However, in large fields,crops are cut by a motorized machine called harvester.Threshing:-It is the process of separating the grain from harvested crops. It is done totake the grains from its outer covering called chaff.

1) In traditional method of threshing, the harvested crop is spread on theground in a small area and various cattle like oxen, cows, buffaloes aremade to walk over it again and again.

2) Beat the crops against wooden logs which also help in separating grainsfrom crops.

3) In larger farms, a motorized machine called thresher is used.WinnowingIt is the process of separating the grains from chaff and hay. This can be doneby means of wind. Here we drop the grains from a certain height and thegrains being heavier fall directly towards the ground while as hay beinglighter is carried away by wind and they make a separate heap. Then thegrains bearing hard cover are difficult to separate from cover. So, the separateprocessing of those grains is carried in industries or factories using specialmachines. The grains are put in machines where they are separated from thehard cover and after reaching the end part of the machine a big fan is kept toeasily throw away the hard separated cover. In this way the grains arecompletely made clean and free from dust and other waste materials. Thesedays combines are being used in large farms for harvesting, threshing andwinnowing. A combine is a huge machine which cuts the standing crops,threshes it and separates the chaff from grain in one operation.Storage of food grains:


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The food grains obtained by harvesting the crops are dried in the sunshinebefore storing to reduce their moisture. It is necessary to prevent theirspoilage during storage because the higher moisture content in the foodgrains promotes the growth of fungus and moulds the stored grains. Thefarmers store the dried food grains at home in metal bins and the bags. Driedneem leaves are used for storing food grains at homes, large scale storage offood grains is done in two ways:

1) In gunny bags2) In grain silos

Legend school of education, kanitar, saderbal. Class 8th, u3

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The most common method of storing food grain on large scale is to fill them in gunnybags, stitch the mouth of gunny bags tightly, and keep these gunny bags one over theother in big godowns. Pesticide solutions are sprayed on the stacked gunny bags inthe godown from time to time.Grain silos are also used for storing food grains on large scale. The grain silos arespecially designed big and tall cylindrical structures which have inbuilt arrangementsfor protection of stored food grains from pests and micro-organisms.Plant breeding:- The science of improving the genotype (the genetic make-up) ofplants by improving their genetic capacity is called plant breeding.There are 4 main plant breeding techniques:i) Introduction:- The seeds of a plant species having some special features are broughtfrom some other place and .grown in a 'new place where it was not grown before. Thisis called introduction.ii) Selection:- Selection is the oldest method of crop improvement. During selection,the individual plants or groups of plants having the desired characters are picked upfrom a population and eliminating the undesirable ones. These selected plants areallowed to reproduce.Selection of plant species is done for useful characters such as disease resistanceresponse to fertilizers, product quality and quantity.iii) Hybridisation:- It is a technique of plant breeding in which two plants havingdesired characters are made to cross and develop seeds. During this process, one plantis considered as male and the other is considered as female. The stigma of the femaleplant is dusted with the pollen grains of the male plant. After pollination, the fusion ofdesired male and female gametes produce embryo having the characters of both theplants.iv) Genetic engineering:- It involves the transfer of one or more genes from one plantto another. The plant in which the foreign gene has been produced is called geneticallymodified plant.Aims and Objectives of plant breeding;High yield and improved quality: Plant breeding techniques are used lo increase theproductivity and to improve the quality of the plant i.e. to make them disease resistantetc. •Biotic and abiotic resistance:- Under natural conditions, the crop plants are prone tocertain biotic and abiotic stresses. Biotic stress includes diseases caused by bacteria,fungi etc. abiotic stress includes damage caused due to flood, frost, heat, salinity, hailetc. Plant breeders try to develop varieties which are resistant to the stresses.Desirable characters:- Plants are grown according to our needs. Plant breeders try todevelop the varieties with desirable characters such as high yield, disease resistant.Development of new (novel) varieties: Seedless tomatoes, stoneless plums and peachesare some of the products that are available to us through the advent of plant breedingtechnique.Soil Improvement:- After the land has been cultivated for a long time, soil nutrients are


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used up. One of the methods of replenishing the nutrients is to add manures andfertilizers. Some other natural methods are as follows:Fallow method:- The old method of allowing the soil to replenish the lost nutrientswas to leave it free for one or more seasons. The decomposition of dead plants andanimals replenish the lost nutrients. However, due to high demand of food grains thismethod is no longer followed.Crop rotation:- Each crop uses more of one element and less of another. Some farmersalternate crops so that land is not drained of any one nutrient. This is called croprotation e.g. after a season of growing rice which uses up nitrogen in the soil, aleguminious plant can be grown which regenerates nitrogen in the soil.

Advantages of crop rotation:1. It reduces the need of fertilizers.2. Several crops may be grown in succession with only one soil preparation.3. It controls pests and weeds.4. By this method, the soil is utilized completely.

Mixed or multiple cropping:- Sometimes two or more crops are grown in the same field.If the crops are chosen properly the products and waste materials of one crop help, inthe growth of other crop and vice versa e.g. cotton and groundnut are grown together.Advantages of multiple cropping:

1. The risk of total crop failure due to uncertain monsoon is reduced.2. Farmers tend to harvest a variety of products at the same time.3. Fertility of the soil is improved.4. Chances of pest infections are greatly reduced.

Intercropping: It is the process of growing two or more crops simultaneously in a samefield in definite row pattern with the objectives of increasing productivity per unitarea. The practice of intercropping is adopted by farmers where they have least accessto irrigation, it is the improved version of mixed cropping.Advantages of intercropping:

1. It makes better use of natural resources.2. Soil erosion is effectively arrested.3. Different crop that are grown are harvested and threshed separately.4. The product of each crop can be marketed and consumed separately.

Differentiate between Mixed cropping and Intercropping:Mixed Cropping IntercroppingIt has target to minimize risk of cropfailure.

It has target production to increaseper unit area.

Seeds of two crops are mixed beforesowing.

Seeds of two crops are not mixed.

It involves no definite pattern of rows It involves a definite pattern of


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of crops. crops.Threshing and harvesting is not doneseparately.

Threshing and harvesting is doneseparately.

Dairying: An establishment where milk and cream are kept and butter and cheese aremade is known as a "DAIRY". The business of dairy is called dairying. The mostimportant dairying areas of the world are in Western Europe, North America and thetemperate parts of the Southern Continents.' The leading producers of cow-milk areIndia, USA, Russia and Germany. India, Sudan and China are the leading producers ofbuffalo milk. The leading producers of cheese are USA,France and Germany and thatof butter and ghee are India, USA and Germany.Man has been keeping animals since times immemorial. We keep some animals forspecific purposes. For instance, milk and milk products are obtained from cattle.Horses, camels and bullocks are used for transportation. Bullocks are also used inagriculture. Cattle dung is used as manure.Also,animal skin is utilized for making avariety of leather goods. Sheep are used for wool and meat. Dog has been used byman for a variety of purposes, like security, and company as a pet.Animals provide us milk, egg, meat, honey, silk and a number of other useful products.The animals like crops are raised on a large scale in "Farms" Milk-yielding animals arecalled the Milch animals e.g. cow, buffalo, goat etc. We get milk from them which isused to prepare various foods like butter, curd, cheese, ghee. etc. The keeping ofanimals for specific purposes is known as "Domestication". All domestic useful animalsconstitute the "Live stock". Cattle, buffaloes, sheep, pigs and camels constitute the livestock wealth of our country. "Animal husbandry" is the field dealing with the study offood, shelter and health care of domestic animals.Feeding:- The feed normally given in a dairy farm is a mixture of ordinary grass and alegume with clover.Heeding:- The proper care, maintenance and management of animals is called asheeding". The health of a live stock is maintained with the proper caring .day andnight. Some very simple practices are followed by farmers for caring their animals.These are:

1. Providing the animals food regularly and properly.2. Erecting the sheds away from human habitations to maintain sanitary

conditions and cleaning the sheds regularly.3. Cleaning the animals regularly.4. Watching the animals carefully to see if they are normal and healthy.5. Taking precautions against infections and some diseases like foot and mouth

disease, cow pox, tuberculosis, anthrax (Splenic fever).6. Working calmly and treating them gently and not frightening the animals.7. Performing regular checkups of the animals by specialists called veterinary

doctors.Poultry:- The term poultry refers to chickens, ducks, turkeys, geese, swans, guineafowl, pigeons, ostriches, and other game birds. In India, chicken is the most common


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domestic bird. Thus, the practice of keeping and breeding of useful animals whichprovide meat and egg is called as "Poultry".Fowl may be classified on the basis of utility, economic value and these include

a) Meat Type (b) Egg Type (c) Dual purpose (d) Game (e)Ornamental and (f) Bantam. They are further classified on the basis of

(i) Class (ii) Breed (iii) Variety, and (iv) Strain.Poultry Feed: The common feed of poultry chicken includes grains, oil-cakes, green-feed and limestone. Limestone helps in the digestion of food and in the formation ofegg shells. For proper egg production, a lot of water is needed by the poultry birds.Domestication of group of birds such as chickens, geese, turkey and duck for thepurpose of obtaining eggs and meat from them is known as "Poultry- Farming"Poultry Housing:- Proper housing for the birds is must in poultry farming. Followingjoints should be kept in mind while housing the birds.

a) The shelter for poultry birds should be comfortable and safe.b) They should be provided with well- ventilated, dry, properly lighted houses.c) Birds of different ages should be kept separately.d) The birds should be protected from the cold winds and heavy rains.e) The houses (pens) are generally made of metal or wood because mud houses

may be attacked by rats or snakes.f) The houses should be regularly cleaned and cleared of excreta and decaying

vegetable materials.g) Good drainage system is must to keep the poultry clean.

Egg Laying: Hen starts laying egg when about six months old. The egg laying bird isknown as "Broody hen".An egg needs to be hatched to develop and grow into a chick. In nature, the motherhen sits on the eggs and keeps them warm. This is known as "Incubation". Warmth soprovided aids in hatching.In poultry farms, hatching is done in "Incubators" called "Hatcheries". The egg hatchesin 21days.Protective Measures against Disease: Poultry birds suffer from diseases such as fowlcholera, chickenpox and rani-khet. These diseases can be fatal. Besides these, the birdsmay get infected with various internal and external parasites. As a preventive measurevaccination and drugs should be given and the infected birds should be separatedfrom the rest.A broiler is a young chicken that grows very fast and can be marketed at the age of 8to12 weeks. It attains about 1.5 kg live weight within this period.Fisherie s(Pisciculture):Rearing and management of fish on a large scale is known as "fisheries". The Indiansubcontinent is surrounded on three sides by water and the coastal area provides arich haul fish. They are a major source of animal protein. Now-a-days, fish arecultivated on industrial scale in large water-reservoirs.Fishery is flourishing industry in our country. Prawns, lobsters, shrimps and edible


Page 35

Oysters are exported on a large-scale. Fish not only provide protein but the oil of thefish can be used for various purposes. Corals are used as decoration pieces. Pearlsfrom oysters are used in jewellery. Some important fishes are Catla, Labeo, Scoliodon,Barbus, Ray fishes and Tuna cod. Marine fishes found in India are Hilsa, Sardine andMackerel etc.Fishes Found In Jammu and Kashmir:- A variety of fishes are found in Jammu andKashmir state. There are 35-species of fish found in the Kashmir valley alone. TheJammu and Kashmir fisheries department has introduced following carps and troutsin ponds and streams of J&K:-

a) Rohu (Labeo rohita)b) Mrigal (Cirhina mrigal)c) Brown troutd) Grass carp.e) Rainbow trout.f) Scale carp.g) Mahseer etc. .

Important fish farms in J&K state are: Harwan, Achabal, Kokernag, Laribal , Daachgam,Manasbal. etc.The pollution of water causes great harm to the fish. This is very serious problem forthe farmers because the fish dies when water body gets polluted. In order to maintaina fish regular monitoring of the level of oxygen and carbon dioxide is essential.Honey bee-- Apis (Apiculture):Honey bees are social insects known for producing honey and the bees wax, and forliving in very highly organized colonies. These feed upon nectar and pollens offlowers. Sucking and chewing mouth parts and undergo complete metamorphosis.Each colony has its own nest called honey comb or beehive. Apiculture is the practiceof keeping beehives and rearing honey bees to get honey and wax. Honey is anessential ingredient of many medicines. Wax is also of great value. The place used forrearing of honey bees is called an apiary. Honey is extracted by a honey extractor. Itcontains 17% and 78% sugar with minerals and enzymes which help in digestion offood. Honey supplies millions of kilograms of honey and beeswax. Beewax is used inmaking candies, creams, polish, cosmetics etc. Honey is a natural antiseptic andvaluable tonic for human body. It prevents infection if applied to a wound. It is alsoused to cure ulcers. A number of Ayurvedic medicines are taken with honey. Eachbeehive harbours a colony of thousands of polymorphic bees, all belonging to a singlefamily. The polymorphic individuals are of three main types:

a) A single queen (fertile female)b) One to a few hundred drones (fertile males)c) Thousands of worker bees (sterile females)

Queen: She is the Supreme being in a colony because all the main activities in the hiverevolve around her. She normally lives about five years and does nothing exceptlaying eggs. She lays about 15 lakh eggs during her life time. Normally 1000-3000


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eggs are laid per day.Drones:- These are quite smaller but stouter than the queen with broader abdomenhigher appendages and larger wings, brain and eyes. These also lack salivary andwax glands and depends for food upon worker bees. These even lack a sting andhence have defense. During breeding season, drones are well fed by the workers andcan be often flying near the hive, chasing and mating with young queens in flight.After mating they are made to leave the hive to save honey.Workers:- These are considerably darker and smaller but most robust with strongestmouth parts and well developed wings. Their body is densely covered with hair likebristles. They are females which develop from fertilized eggs but they cannotreproduce.Textual Book QuestionsQ) Name the following…………Ans) Five requirements essential for obtaining good crop productions are:

a) Right kind of soil.a. Good quality of seedsb. Required amount of waterc. Protection from weeds and pestsd. Proper implements

b) Two types o f fertilizers are:a. Ureab. NPK fertilizers

c) Chemicals used to protect crops from insects, pests and weeds area. Insecticides (Pesticides)- Malthion- Dimecron-poly thionb. Weedicides:-2, 4- D/ siniazine

d) Animal products are:a. Meat, milk, eggs, honey, silk, wool, wax etc.

e) Members of colony of bees are:a. Workers (sterile females) .b. Drones (fertile males)c. Queens (Fertile females)

Q2) Fill in the blanks: Do it yourselfQ3) Answer the following question in only one word or in figure:

1. What is the process of turning and loosening the soil called?a. Ploughing

2. Which implements is used for tilling soil?a. Ploughs

3. Which implements is used for breaking up the large lumps of soil?a. Wooden plank or iron leveller

4. What is the implement used for sowing called?a. Seed drill

5. What is the top part of the drill called?


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a. Seed bowl6. What is an egg laying bird called?

a. Broody hen7. Name the members of bee colony?

a. Worker drone and queen8. Which material is used to cover the floor of a hen house?

a. Straw9. Which is the common food of poultry chicken?

a. Grains10. Which bee is responsible for laying eggs?

a. Queen beeQ4) Give the scientific reason for the following:

a) Grains, pulses, vegetables and fruits should be used in our daily life?a. These form the constituents of the balanced diet for maintaining the

proper well being of the man's body.b) The soil should be loosened before seeds are sown?

A) Loosened soil is better ventilated and suitable for the growth of tiny plant living init, it also allows the roots to penetrate freely and deeper.Q) Seeds should be sown at a proper depth in the soil?A) Because, if they are sown too deep, they will be able to germinate and are sown at a

shallow depth, then they will be eaten by birds and animals.Q) Fruits and vegetables should be washed thoroughly before eating?A) Because, they have a coating of pesticides, otherwise they are harmful to our body.Q) Grains are dried thoroughly before they are stored?A) Grains are dried thoroughly before storing because moisture and humiditypromotes the growth of fungi or moulds on grains. Some of these micro-organism arepoisonous.Q) Answer the following questions:i) What are the requirements of farming which would lead to high yields of crops?A. The basic requirements for growing a crop in an area are as follows:a) proper types of soil b) use of manures c)irrigation d) Better varieties of seeds

e) agricultural tools f) Chemicals to prevent diseases of the plant cropQ) What is tilling? How is it done?A)Tilling or ploughing: The process of loosening and turning the soil is called tilling orploughing. For ploughing the soil various types of ploughs are usedPlough: This is being used for tilling of soil, adding fertilizers to the crop, removing thefeeds, scrapping of soil etc. It is made of wood and drawn by a pair of bulls. It containsa strong triangular iron strip called plough. The main part of plough is log of woodwhich is called as plough shaft. There is a handle on one end. The other end isattached a beam, which is hung on the neck of bulls. One pair of bulls and a man caneasily operate the plough.


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iii) Write a short note on the process of "Sowing"A) Sowing:- It is the process of putting seeds in the soil. There are twomethods of sowing of seeds.Broad Casting:- The sowing of seeds is done manually by spraying in thefield is called broad casting.Seed drill:- A seed drill consists of a vertical tube, with a Seed bowl.This arrangement is tied to the back of a plough. The drill deposits seeds at regularintervals which ensure more accurate sowing of seeds.

Physics

Topic: Some Natural PhenomenonIntroduction:- Some natural phenomenon cause a lot of damage and destruction tohuman life and property. These include cyclones, volcanoes, tsunami storms,earthquakes and lightning. We will discuss two destructive natural phenomenonlighting and Earthquakes. For understanding lightning we should know about electriccharges because lightning is an electric spark on a huge scale which is caused by theaccumulation of electric charges in the clouds.

Electric Charge and Its Discovery:- Electric charge is a property of matter which isresponsible for electrical phenomena. Electric charges exist in two forms: Positiveelectric charge and Negative electric charge.

It was about 2500 years ago, a Greek scientist called Thales observed that when amaterial known as "Amber" was rubbed with a silk cloth, it started attracting tinyfeathers. Amber was actually a hardened translucent yellow brown solid secretion ofcertain trees. In 1600 Dr William Gilbert discovered that things like glass, diamond,wax when rubbed with a cloth, showed the same properties as amber. Thus he coinedthe terms like electric and electricity. Gilbert is called the "Father of Electricity'. Theexistence of electric charges can be shown by performing simple activities like:i) Rubbing a plastic comb with dry hair, makes the comb charged which can thenattract bits of paper.ii) Rubbing a glass rod with a silk cloth, makes the rod charged which enables it toattract pieces of paper.iii) Rubbing a balloon with woolen cloth also produces similar effect.While such activities are done, a kind of force which can attract as well as repel objectsgets developed. This force is called electrostatic force. The charges here remainstationary on the charged body and hence are called static charges. Thus, a bodyhaving electric charge on it is called a charged body and if this charge is not allowed toflow, it is called static electricity.Q) How do objects get charged (Modern Electronic Theory of Electrification)?


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In order to understand the nature of electricity, we need to understand the matter:-i) All matter is made of tiny particles known as atoms. An atom consists of 3 subatomic particles-protons.electrons and neutrons.ii) A proton carries a positive charge, an electron carries a negative charge and theneutron has no charge.iii) The central part of an atom is the nucleus which contains protons and neutrons.The electrons revolve around the nucleus in circular paths called orbits or shells.iv) The electrons present in the outermost orbit are called valence electrons. Thesecan be removed or transferred easily, from one atom to another.v) The transfer of electrons is responsible for charging of bodies.vi) In an atom, the no. of protons are equal to no. of electrons. An atom is electricallyneutral.vii) When an atom gains electrons there are excess of negatively charged electronsthan protons. Hence the body is said to be negatively charged.viii) When an atom loses electrons there is deficiency of electrons than protons. Hencethe body is positively charged.ix) Atoms carrying electric charge are called ions.x) Ions are electrically charged particles and are surrounded by an electric field.xi) Charged particles exert a force on one another, even when they are not in physicalcontact because of their electric field.Thus, it is the movement of electrons from one atom to another, which causes a bodyto get charged. When a glass rod and a piece of silk cloth are rubbed against eachother, the glass rod loses electrons to the silk cloth because the electrons in theoutermost orbits of glass rod are loosely bound as compared to those in the silk cloth.Now the glass rod has a deficiency of electrons and is positively charged while the silkcloth has excess of electrons and hence is negatively charged.

Similar is the process due to which other bodies like balloon, comb etc. get charged.Whether an object lose electrons or gain electrons during rubbing depends on thenature of the object. The materials like glass, woolen cloth, hair and ball pen refill loseelectrons more easily and hence get positively charged on rubbing. on the other hand,the materials like silk, rubber, balloon, plastic comb, polythene gain electrons moreeasily and hence get positively charged on during rubbing.Interaction of Electric Charges:There are two types of charges:- Positive charges and negative charges. A positivecharge repels another positive charge, but a positive charge attracts a negative charge.Thus, it can be concluded like charges attract each other and unlike charges repel eachother.Many times when we take off woolen or synthetic clothes (like polyester and nylonclothes), our body hair stands erect on their ends. This is because rubbing (or friction),while taking off these clothes, charges the body hair with the same kind of electric


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charge. Due to their like charges, the body hairs repel one another. This repulsionmakes the body hair stand erect.

1. When a charged glass rod (rubbed with silk) is brought near a charged plasticstraw there is attraction between the two. What is the nature of charge on theplastic straw?

a. Since the charge present on a glass rod (rubbed with silk) is said to bepositive. There can be attraction between a charged glass rod and acharged plastic straw is negative.

2. Why a charged objects attracts an uncharged object?a. A charged object attracts an uncharged object by electric induction. As an

example, we will explain how a charged plastic comb attracts an-uncharged piece of paper. Suppose a negatively charged plastic comb isheld over a small piece of paper. Suppose a negatively charged plasticcomb is held over a small piece of paper. The negatively charged plasticcomb produces opposite charges (positive charges) in the top end of paper(which is nearer to it) by electric induction. This is because negativecharge of plastic comb repels the electrons from the top side of paper to itsbottom side leaving the top side of the paper positively charged. Theplastic comb has negative charge and the top of paper has now positivecharge. The attraction between opposite charges (negative charge onplastic comb and positive charge on top of paper) results in the paperbeing attracted by the plastic comb.

Electroscope:- An electroscope is a device for detecting electric charge on an object. Byusing an electroscope, we can tell whether an object is electrically charged or not. Itwas the first electrical instrument. It was invented by British physician WilliamGilbert. It is very sensitive and delicate instrument. The gold leaf electroscope and thepith ball electrosope are the two widely used electroscopes in physics laboratory.Construction of Gold Leaf Electroscope:-It consists of a brass rod which passes through an insulator plug in a glass case.The topend of the brass rod carries a brass disc or cap and the lower end carries two thin goldleaves. Thin gold leaves are very delicate and sensitive to detect even a very smallcharge. The glass case protects the leaves from outside air current. The lower part ofthe glass case is surrounded by a metal foil from inside. When the electroscope isused the metal foil is earthed. It helps the charge to stay on the gold leaves for alonger time.Working Of Electroscope:- In order to detect the electric charge on an object, we touchthe metal top of the electroscope with their object and observe the leaves of theelectroscope. If they diverge (or open up), then the given object has an electric chargeon it (or given object) is electrically charged, if on touching the metal top ofelectroscope with the given object, the leaves of the electroscope do not diverge (donot open up) then the given object has no electric charge on it (it has no electric chargeon it or the given object is electrically natural).


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If we touch a charged electroscope with our finger, it gets discharged and its leavescollapse. Actually on touching the electric charge present on the electroscope flows tothe earth through our hand and body and this is known as Earthing. Thus the processof transferring an electric charge from a charged object to the earth is called earthing.Earthing is provided in the wiring of houses and other buildings to protect us fromelectric shocks who may occur due to any leakage of electric current from the body ofan electrical appliance. Metal wires (called earth wires) are used for this purpose.Electric DischargeThe passage of electric current in air due to movement of electric charges is calledelectric discharge. During electric discharge, the positive and negative electric chargescancel out each other and an electric spark and a cracking sound are produced. Innature, electric discharge within a cloud during thunderstorm produces huge electricsparks known as lightning along with a loud sound called Thunder.Lightning: The electrical phenomena occurring in atmosphere due to transfer ofcharges from cloud to earth is called lighting.How Lightning Takes Place:- Lightning is the electric discharge. When air blows frombottom to top in. clouds electric charges are developed due to friction. Clouds aremade up of water molecules and dust particles. These molecules are of different sizes.When air blows, the molecules of cloud are rubbed against each other and because ofthese bigger molecules get negative and small molecules get positive charge. Due tomass difference, small molecules take the top. Positive are big molecules take lowerposition of the cloud. In this way a cloud (storm cloud) gets charged when theaccumulation of negative charges is very much, then the air between the storm cloudand earth is ionized and charges rush down from thunderstorm to earth. Whiledischarging the air is heated up and because of which we see the Hash of light and alsoair expands and because of which we hear the sound in the form of thunder. In thisway, lightning and thunder takes place. The electrical nature of lighting wasestablished by Benjamin Franklin.

Dangers and ProtectionLighting causes great damage and destruction to living organisms including tallbuildings and trees. The potential difference created between clouds and earth is 2xl07

-108 volts and hence is very dangerous.Following steps help us to protect us from lighting:1. We should remain inside the house.2. If travelling remain inside the vehicle.3. Do not take shelter under big trees.4. Do not lie on the ground while lightning.5. We should avoid raising an umbrella over our head.6. We should switch off our T V sets.7. We should not touch metal pipes fixed in a house or building.8. We should stay away from electric poles, telephone poles and other metal objects.


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9. Tall buildings should use lightning conductors.Lighting Conductor:- It is a device used to save buildings from lighting strokes, itconsists of a thick metal strip (copper) which is fixed above the highest point of abuilding. Its upper end is in the form of spikes and lower end is joined with a copperplate which is inside the earth. As the thunderstorm passes over the building, itinduces positive charges on spikes and repels negative charges which get accumulatedon the metal plate.The electric energy of the lightning passes through the metal strip and gets dischargedsafely into the ground. Thus the conductor protects against lightning by conductingthe electric energy of lightning into the earth.Earthquake:- The sudden shaking of earth for sometime due to release of energy insidethe earth is called earthquake, it is a natural phenomenon which can't be predicted inadvance. This makes the even more dangerous. Due to the release of energy inside theearth, there is a formation of wave which moves through the earth and causes shakingof earth or earthquake.Q) Why do earthquakes occur?a. Earthquakes occur due to

i) Sliding of plates ii) Colliding of platesi) The earth has three main layers core, crust and mantle. The mantle contains solidand molten dense rocks. Due to convection currents in the mantle, the plates of thecrust have very small motion. They are slowly sliding in the opposite directions. Thismotion creates a lot of pressure on the plates. When the contact points between theplates are broken, a strong jerk is produced causing the release of lot of energy. Thisenergy produces seismic waves which travel through earth causing earthquake.ii) Focus:- The point inside the earth where earthquake originates. Epicenter:- Thepoint above the focus on the surface of earth is called epicenter.ii) Colliding of plates: - When the two plates collide with each other head on, then theends of these crust plates buckle and fold forming new mountains and causingearthquake. The zones which are most prone to earthquakes are called Seismic zones.Seismograph:- It is an instrument which measures and records the magnitude of anearthquake in terms of shock waves it produces. It is also known as Seismometer.Construction:- It consists of a heavy weight suspended from a support with the help ofa strong wire. The support is attached to the base of the seismograph. The base of theseismograph is fixed rigidly to a solid rock on the surface of the earth. A pen isattached to the lower end of the hanging heavy weight. This pen can trace lines on agraph paper wound around a rotating drum which lies beneath it.Working:- When an earthquake occurs the earth starts shaking due to which the baseof seismograph fixed to the earth also starts shaking. But the freely suspended heavyweight and the pen attached to it do not shake during earthquake, they remainstationary. Since the graph paper on the rotating drum shakes with the shaking earth,the pen attached to it records the vibrations produced by the earthquake on a graphpaper which moves under it. The record/ graph obtained from a seismograph is called


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Seismogram.Richter scale:- The magnitude of an earthquake is expressed on a Richter scale. It is aseries of numbers from 1-12 used to express the magnitude of an earthquake.Earthquakes with magnitude greater than 7 are really destructive.Precautions against Earthquakes:

1. All the houses and buildings in seismic zones should be designed andconstructed in a way so that they can with stand major earthquake tremors.

2. Heavy construction material like iron etc should be avoided in seismic zones.3. Cupboards and shelves should be fixed to the walls so that they do not fail easily.4. During an earthquake, buildings may catch fire, so fire fighting equipments

should be in working order.5. During an earthquake, take shelter under a table.6. If we are in car, we should drive it slowly and take it to a clear spot.7. We should always have a first aid box ready.

Note:- After studying the chapter thoroughly, do not textual questions on your fairnote books. Draw a neat and well labeled diagram of:

i) An electroscopeii) A Seismograph

Textual Questions1. Sometimes, a crackling sound is heard while taking off a sweater during winters.

Why?a. Sweater is made of wool and there is a constant friction between the

sweater and the inner shirt. Because of this friction there occurs transferof electrons from one body to another. When we take off the sweater,these two bodies attract each other and the passage of electrons throughthe air in the form of spark let out heat and sound energy. Thus, we hearthe crackle sound and in the dark room we may see the spark lights aswell.

2. Explain why a charged body loses its charge if we touch it with our hands.a. When we touch a charged body with our hand, they excess charge present

on the body get transferred to the ground through our body. Thus, thecharged body loses its charge and becomes neutral.

3. Name the scale on which the destructive energy of an earthquake is measured. Anearthquake measures 3 on this scale .Would it be recorded by a seismograph? Is itlikely to cause muchdamage?

a. The destructive energy of an earthquake is measured on Richter scale. Yes,the earthquake of magnitude 3 will be recorded by seismograph, but is notlikely to cause much damage. Generally, earthquake of magnitudes higherthan 6are considered to be destructive in nature.

4. Suggest three measures to protect ourselves from lightning


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a. We should remain inside the house.b. We should switch off our T.V. sets.c. If travelling remain inside a vehicle.

5. List three states in India where earthquakes are more likely to strike.a. The three states in India where earthquakes are more likely to strike are

Jammu and Kashmir, Gujarat and Assam.6. Suppose you are outside your home and an earthquake strikes. What precaution

would you take to protect yourself?a. Do not remain under big tree or pole.b. We should try to move in an open space.c. If you are in a car, remain inside it.

7. The weather department has predicted that a thunder storm is likely to occur ona certain day. Suppose you have to go out on that day. Would you carry anumbrella? Explain.

No, we won't an umbrella in a thunderstorm. It is because thunderstorm isaccompanied by lightening and electric discharge from the clouds and it can travelthrough the metallic rod and this may give an electric shock to a person who iscarrying it. Hence, it is not safe to carry an umbrella during a thunderstorm.

8. Describe with the help of a diagram an instrument which can be used to detect acharged body.

a. It consists of a brass rod which passes through an insulator plug in a glasscase. The top end of brass rod carries a basic disc or cap and lower endcarries two thin gold leaves. The gold leaves are very delicate andsensitive to detect even a small charge. The glass protects the leaf fromoutside current. The lower part of glass case is surrounded by a metal foilfrom inside. When the electroscope is used the metal foil is earthed. Ithelps the charge to stay on gold leaves for longer time. In order to detectthe charge on an object we touch the metal top of an electroscope withthat object and observe the leaves of electroscope. If they diverge (or openup), then the object has a electric charge on it or given object is electricallycharged if, the leaves of electroscope do not diverge (do not open up) thenthe given object has no charge on it (or the given object has no electriccharge) (Or the given object) is electrically un charged.

Textual Questions1. Which of the following cannot be charged easily by friction?...........

a. Only non-conducting materials can be easily charged by friction. Copper isa highly conducted materials. Therefore, a copper rod cannot be chargedeasily by friction.

2. When a glass rod is rubbed with a piece of silk cloth the rod……………a. The rod becomes positively charged, while the cloth has a negative charge.

When an object is charged by rubbing it against another object, the twoobjects get oppositely charged. By convention, it is considered that the


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charge acquired by the glass rod is positive and charge acquired by thecloth is negative. Therefore, the rod becomes positively charged and thecloth becomes negatively charged.

3. Do it yourself4. Sometimes, a crackling sound is heard while taking off a sweater during winters.

Why?a. When a sweater is taken off the woolen sweater gets charged because of

the friction between the sweater and the body. Hence, one can hear acrackling sound during the given process.

5. Explain why a charged body loses its charge if we touch it with our hands.a. When we touch a charged object, our body conducts its charges to the

earth. That is why a charged body loses its charge, if we touch it with ourhands. This phenomenon is known as electric discharge.

6. Name the scale on which the destructive energy of an earthquake is measured. Anearthquake measures 3 on this scale. Would it be recorded by a seismograph? Is itlikely to cause much damage?

a. The destructive energy of an earthquake is measured by the Richter scale.This scale has the readings from I to 10.The reading of magnitude 3 on the Richter scale would be recorded by aseismograph. If the Richter scale gives a reading of magnitude 3, then theearthquake is not likely to cause much damage. Generally, earthquake ofmagnitudes higher than 5 is considered destructive in nature.

7. Suggest three measures to protect ourselves from lightning.a. Protective measures against lightning are as follows:

i. Stay in a completely closed place. If you are moving in a car, thenremain there until the lightning is over. Close the windows of the carimmediately.

ii. Do not touch any electrical wires, telephone cables, metal pipes, etc.iii. Do not bath in running water. This may cause an electric shock.

8. Explain why a charged balloon is repelled by another charged balloon whereasan uncharged balloon is attracted by another charged balloon?

a. The nature of charges present on the surface of charged balloons aresimilar. Since like charges repel each other, two charged balloons repeleach other. When a charged body is brought near an uncharged body, theuncharged body acquires charges on its surface caused by the induction ofcharges. The charges are of opposite nature in relation to the chargedbody. Since unlike charges attract each other, a charged body alwaysattracts an uncharged body. Hence, an uncharged balloon is attracted byanother charged balloon.

9. Describe with the help of a diagram an instrument which can be use to defect acharged body.

a. An electroscope can be used to detect whether a body is charged or not.


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The figure shows a simple electroscope (fig 17.4 page no. 213). It consistsof a metal rod. At one end of the rod, two leaves of aluminium foil are fixedand at the other end. there is a metal disc. The leaves of aluminium foil areplaced inside a conical flask and the flask is corked to isolate the leavesfrom air. When the metal disc is touched with a charged body, thealuminium strips move away from each other. This happens because somef the charges of the body are transferred to the strips through the metalrod. This method of charging a body is called charging by conduction. Thenature of charges on both the leaves and the charged body are similar.Hence, both the leaves of the aluminium foil will move away from eachother. If the body was .not charged, then the leaves of the foil wouldremain as they were before. They would not repel each other.

10. List three states in India where earthquakes are more likely.a. The three states in India where earthquakes are more likely to strike are

Jammu and Kashmir. Gujarat and Assam.11. Suppose you are outside your home and an earthquake strikes. What precaution

would you take to protect yourself?a. Suppose we are outside your home and an earthquake strikes us some of

the precautions taken to protect ourselves are as follows:i. Try to find an open field away from tall buildings, installations, tall

trees, and electric wires and poles.ii. If travelling in a bus or a car then do not come out when an

earthquake strikes. Ask the driver in an open field.

Algebra

exercise 9.1 Question 1:

Identify the terms, their coefficients for each of the following expressions. (i) 5xyz2 − 3zy

(ii) 1 + x + x2

(iii) 4x2y2 − 4x2y2z2 + z2

(iv) 3 − pq + qr − rp

(v)

(vi) 0.3a − 0.6ab + 0.5b Answer:

The terms and the respective coefficients of the given expressions are as follows.

- Terms Coefficients

(i) 5xyz2

− 3zy

5

− 3

(ii) 1

xx2

1

1

1

(iii) 4x2y2 −

4x2y2z2

z2

4

− 4

1

(iv) 3 −

pqqr

– rp

3

−1

1

−1

(v)

−xy − 1

(vi) 0.3a

− 0.6ab

0.5b

0.3

− 0.6

0.5

Question 2:

Classify the following polynomials as monomials, binomials, trinomials. Which polynomials do not fit

in any of these three categories? x + y, 1000, x + x2 + x3 + x4, 7 + y + 5x, 2y − 3y2, 2y − 3y2 +

4y3, 5x − 4y + 3xy, 4z − 15z2, ab + bc + cd + da, pqr, p2q + pq2, 2p + 2q Answer:

The given expressions are classified as

Monomials: 1000,pqr

Binomials: x + y, 2y − 3y2, 4z − 15z2, p2q + pq2, 2p + 2q

Trinomials: 7 + y + 5x, 2y − 3y2 + 4y3, 5x − 4y + 3xyPolynomials that

do not fit in any of these categories are x + x2 + x3 + x4, ab + bc + cd

+ daQuestion 3:

Add the following.

(i) ab − bc, bc − ca, ca − ab

(ii)a − b + ab, b − c + bc, c − a + ac (iii) 2p2q2 − 3pq + 4, 5 + 7pq − 3p2q2

(iv) l2 + m2, m2 + n2, n2 + l2, 2lm + 2mn + 2nl

Answer:

The given expressions written in separate rows, with like terms one below the other and then the

addition of these expressions are as follows.

(i)

Thus, the sum of the given expressions is 0.

(ii)

Thus, the sum of the given expressions is ab + bc + ac.

(iii)

Thus, the sum of the given expressions is −p2q2 + 4pq + 9. (iv)

Thus, the sum of the given expressions is 2(l2 + m2 + n2 + lm + mn + nl).

Question 4:

(a) Subtract 4a − 7ab + 3b + 12 from 12a − 9ab + 5b − 3

(b) Subtract 3xy + 5yz − 7zx from 5xy − 2yz − 2zx + 10xyz

(c) Subtract 4p2q − 3pq + 5pq2 − 8p + 7q − 10 from 18 − 3p − 11q + 5pq − 2pq2 + 5p2q

Answer:

The given expressions in separate rows, with like terms one below the other and then the

subtraction of these expressions is as follows.

(a)

(b)

(c)

Exercise 9.2 Question 1:

Find the product of the following pairs of monomials.

(i) 4, 7p (ii) − 4p, 7p (iii) − 4p, 7pq

(iv) 4p3, − 3p (v) 4p, 0 Answer:

The product will be as follows.

(i) 4 × 7p = 4 × 7 × p = 28p

(ii) − 4p × 7p = − 4 × p × 7 × p = (− 4 × 7) × (p × p) = − 28 p2

(iii) − 4p × 7pq = − 4 × p × 7 × p × q = (− 4 × 7) × (p × p × q) = − 28p2q

(iv) 4p3 × − 3p = 4 × (− 3) × p × p × p × p = − 12 p4

(v) 4p × 0 = 4 × p × 0 = 0 Question 2:

Find the areas of rectangles with the following pairs of monomials as their lengths and breadths

respectively.

(p, q); (10m, 5n); (20x2, 5y2); (4x, 3x2); (3mn, 4np) Answer:

We know that,

Area of rectangle = Length × Breadth

Area of 1st rectangle = p × q = pq

Area of 2nd rectangle = 10m × 5n = 10 × 5 × m × n = 50 mn

Area of 3rd rectangle = 20x2 × 5y2 = 20 × 5 × x2 × y2 = 100 x2y2

Area of 4th rectangle = 4x × 3x2 = 4 × 3 × x × x2 = 12x3

Area of 5th rectangle = 3mn × 4np = 3 × 4 × m × n × n × p = 12mn2pQuestion 3:

Complete the table of products.

2x − 5y 3x2 − 4xy 7x2y − 9x2y2

2x 4x2 … … … … …

− 5y … … − 15x2y … … …

3x2 … … … … … …

− 4xy … … … … … …

7x2y … … … … … …

− 9x2y2 … … … … … …

Answer:

The table can be completed as follows.

2x − 5y 3x2 − 4xy 7x2y − 9x2y2

2x 4x2 − 10xy 6x3 − 8x2y 14x3y − 18x3y2

− 5y − 10xy 25 y2 − 15x2y 20xy2 − 35x2y2 45x2y3

3x2 6x3 − 15x2y 9x4 − 12x3y 21x4y − 27x4y2

− 4xy − 8x2y 20xy2 − 12x3y 16x2y2 − 28x3y2 36x3y3

7x2y 14x3y − 35x2y2 21x4y − 28x3y2 49x4y2 − 63x4y3

− 9x2y2 − 18x3y2 45 x2y3 − 27x4y2 36x3y3 − 63x4y3 81x4y4

Question 4:

Obtain the volume of rectangular boxes with the following length, breadth and height respectively.

(i) 5a, 3a2, 7a4 (ii) 2p, 4q, 8r (iii) xy, 2x2y, 2xy2

(iv) a, 2b, 3c Answer:

We know that,

Volume = Length × Breadth × Height

(i) Volume = 5a × 3a2 × 7a4 = 5 × 3 × 7 × a × a2 × a4 = 105 a7

(ii) Volume = 2p × 4q × 8r = 2 × 4 × 8 × p × q × r = 64pqr

(iii) Volume = xy × 2x2y × 2xy2 = 2 × 2 × xy ×x2y × xy2 = 4x4y4

(iv) Volume = a × 2b × 3c = 2 × 3 × a × b × c = 6abc Question 5:

Obtain the product of

(i) xy,yz, zx (ii) a, − a2, a3 (iii) 2, 4y, 8y2, 16y3 (iv) a, 2b, 3c,

6abc (v) m, − mn, mnp Answer:

(i) xy × yz × zx = x2y2z2

(ii) a × (− a2) × a3 = − a6

(iii) 2 × 4y × 8y2 × 16y3 = 2 × 4 × 8 × 16 × y × y2 × y3 = 1024 y6

(iv) a × 2b × 3c × 6abc = 2 × 3 × 6 × a × b × c × abc = 36a2b2c2

(v) m × (− mn) × mnp = − m3n2p


Carry out the multiplication of the expressions in each of the following pairs.

(i) 4p, q + r (ii) ab, a − b (iii) a + b, 7a2b2

(iv) a2 − 9, 4a (v) pq + qr + rp, 0 Answer:

(i) (4p) × (q + r) = (4p × q) + (4p × r) = 4pq + 4pr

(ii) (ab) × (a − b) = (ab × a) + [ab × (− b)] = a2b−ab2

(iii) (a + b) × (7a2b2) = (a × 7a2b2) + (b × 7a2b2) = 7a3b2+ 7a2b3

(iv) (a2 − 9) × (4a) = (a2 × 4a) + (− 9) × (4a) = 4a3 − 36a (v) (pq + qr + rp) × 0 = (pq × 0) + (qr

× 0) + (rp × 0) = 0 Question 2: Complete the table

--- First expression Second Expression Product

(i) a b + c + d -

(ii) x + y − 5 5 xy -

(iii) p 6p2− 7p + 5 -

(iv) 4p2q2 p2−q2 -

(v) a + b + c Abc -

Answer:

The table can be completed as follows.

- First expression Second Expression Product

(i) a b + c + d ab + ac + ad

(ii) x + y − 5 5 xy 5x2y + 5xy2 − 25xy

(iii) p 6p2− 7p + 5 6p3− 7p2 + 5p

(iv) 4p2q2 p2−q2 4p4q2 − 4p2q4

(v) a + b + c Abc a2bc + ab2c + abc2

Question 3:

Find the product.

(i) (a2) × (2a22) × (4a26)

(ii)

(iii)

(iv) x × x2 × x3 × x4 Answer:

(i) (a2) × (2a22) × (4a26) = 2 × 4 ×a2

× a22 × a26 = 8a50

(ii)

(iii)

(iv) x × x2 × x3 × x4 = x10Question 4:

(a) Simplify 3x (4x −5) + 3 and find its values for (i) x = 3, (ii) .

(b) a (a2 + a + 1) + 5 and find its values for (i) a = 0, (ii) a = 1, (iii) a = − 1.

Answer:

(a) 3x (4x − 5) + 3 = 12x2 − 15x + 3

(i) For x = 3, 12x2 − 15x + 3 = 12 (3)2 − 15(3) + 3

= 108 − 45 + 3

= 66

(ii) For

(b)a (a2 + a + 1) + 5 = a3 + a2 + a + 5

(i) Fora = 0, a3 + a2 + a + 5 = 0 + 0 + 0 + 5 = 5

(ii) Fora = 1, a3 + a2 + a + 5 = (1)3 + (1)2 + 1 + 5

= 1 + 1 + 1 + 5 = 8

(iii) Fora = −1, a3 + a2 + a + 5 = (−1)3 + (−1)2 + (−1) + 5

= − 1 + 1 − 1 + 5 = 4 Question 5:

(a) Add: p (p − q), q (q − r) and r (r − p)

(b) Add: 2x (z − x − y) and 2y (z − y − x)

(c) Subtract: 3l (l − 4m + 5n) from 4l (10n − 3m + 2l)

(d) Subtract: 3a (a + b + c) − 2b (a − b + c) from 4c (− a + b + c) Answer:

(a) First expression = p (p − q) = p2 − pq Second expression =

q (q − r) = q2 − qr

Third expression = r (r − p) = r2 − pr

Adding the three expressions, we obtain

Therefore, the sum of the given expressions is p2 + q2 + r2 − pq − qr − rp. (b) First expression = 2x

(z − x − y) = 2xz − 2x2 − 2xy Second expression = 2y (z − y − x) = 2yz − 2y2 − 2yx Adding the

two expressions, we obtain

Therefore, the sum of the given expressions is − 2x2 − 2y2 − 4xy + 2yz + 2zx.

(c) 3l (l − 4m + 5n) = 3l2 − 12lm + 15ln

4l (10n − 3m + 2l) = 40ln − 12lm + 8l2

Subtracting these expressions, we obtain

Therefore, the result is 5l2 + 25ln.

(d) 3a (a + b + c) − 2b (a − b + c) = 3a2 +3ab + 3ac − 2ba + 2b2 − 2bc

= 3a2 + 2b2 + ab + 3ac − 2bc

4c (− a + b + c) = − 4ac + 4bc + 4c2

Subtracting these expressions, we obtain

Therefore, the result is −3a2 −2b2 + 4c2−ab + 6bc − 7ac.


Multiply the binomials.

(i) (2x + 5) and (4x − 3) (ii) (y − 8) and (3y − 4)

(iii) (2.5l − 0.5m) and (2.5l + 0.5m) (iv) (a + 3b) and (x + 5)

(v) (2pq + 3q2) and (3pq − 2q2)

(vi)

Answer:

(i) (2x + 5) × (4x − 3) = 2x × (4x − 3) + 5 × (4x − 3)

= 8x2 − 6x + 20x − 15

= 8x2 + 14x −15 (By adding like terms)

(ii) (y − 8) × (3y − 4) = y × (3y − 4) − 8 × (3y − 4)

= 3y2 − 4y − 24y + 32

= 3y2 − 28y + 32 (By adding like terms)

(iii) (2.5l − 0.5m) × (2.5l + 0.5m) = 2.5l × (2.5l + 0.5m) − 0.5m (2.5l + 0.5m)

= 6.25l2 + 1.25lm − 1.25lm − 0.25m2

= 6.25l2 − 0.25m2

(iv) (a + 3b) × (x + 5) = a × (x + 5) + 3b × (x + 5)

= ax + 5a + 3bx + 15b

(v) (2pq + 3q2) × (3pq − 2q2) = 2pq × (3pq − 2q2) + 3q2 × (3pq − 2q2)

= 6p2q2 − 4pq3 + 9pq3 − 6q4

= 6p2q2 + 5pq3 − 6q4

Question 2:

Find the product.

(i) (5 − 2x) (3 + x) (ii) (x + 7y) (7x − y) (iii) (a2 + b) (a +

b2) (iv) (p2 − q2) (2p + q) Answer:

(i) (5 − 2x) (3 + x) = 5 (3 + x) − 2x (3 + x)

= 15 + 5x − 6x − 2x2

= 15 − x − 2x2

(ii) (x + 7y) (7x − y) = x (7x − y) + 7y (7x − y)

= 7x2 − xy + 49xy − 7y2

= 7x2 + 48xy − 7y2

(iii) (a2 + b) (a + b2) = a2 (a + b2) + b (a + b2)

= a3 + a2b2 + ab + b3

(iv) (p2 − q2) (2p + q) = p2 (2p + q) − q2 (2p + q)

= 2p3 + p2q − 2pq2 − q3Question 3:

Simplify.

(i) (x2 − 5) (x + 5) + 25

(ii) (a2 + 5) (b3 + 3) + 5

(iii) (t + s2) (t2 − s)

(iv) (a + b) (c − d) + (a − b) (c + d) + 2 (ac + bd)

(v) (x + y) (2x + y) + (x + 2y) (x − y)

(vi) (x + y) (x2 − xy + y2)

(vii) (1.5x − 4y) (1.5x + 4y + 3) − 4.5x + 12y

(viii)(a + b + c) (a + b − c) Answer:

(i) (x2 − 5) (x + 5) + 25

= x2 (x + 5) − 5 (x + 5) + 25

= x3 + 5x2 − 5x − 25 + 25

= x3 + 5x2 − 5x

(ii) (a2 + 5) (b3 + 3) + 5

= a2 (b3 + 3) + 5 (b3 + 3) + 5

= a2b3 + 3a2 + 5b3 + 15 + 5

(vi)

= a2b3 + 3a2 + 5b3 + 20

(iii) (t + s2) (t2 − s)

= t (t2−s) + s2 (t2 − s)

= t3 − st + s2t2−s3

(iv) (a + b) (c − d) + (a − b) (c + d) + 2 (ac + bd)

= a (c − d) + b (c − d) + a (c + d) − b (c + d) + 2 (ac + bd) = ac − ad + bc

− bd + ac + ad − bc − bd + 2ac + 2bd

= (ac + ac + 2ac) + (ad − ad) + (bc − bc) + (2bd − bd − bd)

= 4ac

(v) (x + y) (2x + y) + (x + 2y) (x − y)

= x (2x + y) + y (2x + y) + x (x − y) + 2y (x − y) = 2x2 + xy +

2xy + y2 + x2 − xy + 2xy − 2y2

= (2x2 + x2) + (y2 − 2y2) + (xy + 2xy − xy + 2xy)

= 3x2 − y2 + 4xy

(vi) (x + y) (x2 − xy + y2)

= x (x2 − xy + y2) + y (x2 − xy + y2)

= x3 − x2y + xy2 + x2y − xy2 + y3

= x3 + y3 + (xy2 − xy2) + (x2y − x2y)

= x3 + y3

(vii) (1.5x − 4y) (1.5x + 4y + 3) − 4.5x + 12y

= 1.5x (1.5x + 4y + 3) − 4y (1.5x + 4y + 3) − 4.5x + 12y

= 2.25 x2 + 6xy + 4.5x − 6xy − 16y2 − 12y − 4.5x + 12y

= 2.25 x2 + (6xy − 6xy) + (4.5x − 4.5x) − 16y2 + (12y − 12y)

= 2.25x2 − 16y2

(viii) (a + b + c) (a + b − c)

= a (a + b − c) + b (a + b − c) + c (a + b − c)

= a2 + ab − ac + ab + b2 − bc + ca + bc − c2

= a2 + b2 − c2 + (ab + ab) + (bc − bc) + (ca − ca)

= a2 + b2 − c2 + 2ab


Use a suitable identity to get each of the following products.

(i) (x + 3) (x + 3) (ii) (2y + 5) (2y + 5)

(iii) (2a − 7) (2a − 7) (iv)

(v) (1.1m − 0.4) (1.1 m + 0.4) (vi) (a2 + b2) (− a2 + b2)

(vii) (6x − 7) (6x + 7) (viii) (− a + c) (− a + c)

(ix) (x) (7a − 9b) (7a − 9b)

Answer:

The products will be as follows.

(i) (x + 3) (x + 3) = (x + 3)2

= (x)2 + 2(x) (3) + (3)2 [(a + b)2 = a2 + 2ab + b2]

= x2 + 6x + 9

(ii) (2y + 5) (2y + 5) = (2y + 5)2

= (2y)2 + 2(2y) (5) + (5)2 [(a + b)2 = a2 + 2ab + b2]

= 4y2 + 20y + 25

(iii) (2a − 7) (2a − 7) = (2a − 7)2

= (2a)2 − 2(2a) (7) + (7)2 [(a − b)2 = a2 − 2ab + b2]

= 4a2 − 28a + 49

[(a − b)2 = a2 − 2ab + b2]

(v) (1.1m − 0.4) (1.1 m + 0.4)

= (1.1m)2− (0.4)2 [(a + b) (a − b) = a2 − b2] = 1.21m2 − 0.16

(vi) (a2 + b2) (− a2 + b2) = (b2 + a2) (b2 − a2)

= (b2)2 − (a2)2 [(a + b) (a − b) = a2 − b2]

= b4 − a4

(vii) (6x − 7) (6x + 7) = (6x)2 − (7)2 [(a + b) (a − b) = a2 − b2]

= 36x2 − 49

(viii) (− a + c) (− a + c) = (− a + c)2

= (− a)2 + 2(− a) (c) + (c)2 [(a + b)2 = a2 + 2ab + b2]

= a2 − 2ac + c2

(iv)

[(a + b)2 = a2 + 2ab + b2]

(x) (7a − 9b) (7a − 9b) = (7a − 9b)2

= (7a)2 − 2(7a)(9b) + (9b)2 [(a −b)2 = a2 − 2ab + b2]

= 49a2 − 126ab + 81b2Question 2:

Use the identity (x + a) (x + b) = x2 + (a + b)x + ab to find the following products. (i) (x + 3) (x +

7) (ii) (4x +5) (4x + 1)

(iii) (4x − 5) (4x − 1) (iv) (4x + 5) (4x − 1)

(v) (2x +5y) (2x + 3y) (vi) (2a2 +9) (2a2 + 5)

(vii) (xyz − 4) (xyz − 2) Answer:

The products will be as follows.

(i) (x + 3) (x + 7) = x2 + (3 + 7) x + (3) (7)

= x2 + 10x + 21

(ii) (4x + 5) (4x + 1) = (4x)2 + (5 + 1) (4x) + (5) (1) = 16x2 + 24x + 5

(iii)

= 16x2 − 24x + 5

(iv)

= 16x2 + 16x − 5

(v) (2x +5y) (2x + 3y) = (2x)2 + (5y + 3y) (2x) + (5y) (3y)

= 4x2 + 16xy + 15y2

(vi) (2a2 +9) (2a2 + 5) = (2a2)2 + (9 + 5) (2a2) + (9) (5)

= 4a4 + 28a2 + 45

(vii) (xyz − 4) (xyz − 2)

=

= x2y2z2 − 6xyz + 8 Question 3:

Find the following squares by suing the identities.

(i) (b − 7)2 (ii) (xy + 3z)2 (iii) (6x2 − 5y)2

(iv) (v) (0.4p − 0.5q)2 (vi) (2xy + 5y)2 Answer:

(i) (b − 7)2 = (b)2 − 2(b) (7) + (7)2 [(a − b)2 = a2 − 2ab + b2]

(ix)

= b2 − 14b + 49

(ii) (xy + 3z)2 = (xy)2 + 2(xy) (3z) + (3z)2 [(a + b)2 = a2 + 2ab + b2]

= x2y2 + 6xyz + 9z2

(iii) (6x2 − 5y)2 = (6x2)2 − 2(6x2) (5y) + (5y)2 [(a − b)2 = a2 − 2ab + b2]

= 36x4 − 60x2y + 25y2

(iv) [(a + b)2 = a2 + 2ab + b2]

(v) (0.4p − 0.5q)2 = (0.4p)2 − 2 (0.4p) (0.5q) + (0.5q)2

[(a − b)2 = a2 − 2ab + b2]

= 0.16p2− 0.4pq+ 0.25q2

(vi) (2xy + 5y)2 = (2xy)2 + 2(2xy) (5y) + (5y)2

[(a + b)2 = a2 + 2ab + b2]

= 4x2y2 + 20xy2 + 25y2Question 4:

Simplify.

(i) (a2 − b2)2 (ii) (2x +5)2 − (2x − 5)2

(iii) (7m − 8n)2 + (7m + 8n)2 (iv) (4m + 5n)2 + (5m + 4n)2

(v) (2.5p − 1.5q)2 − (1.5p − 2.5q)2

(vi)(ab + bc)2 − 2ab2c (vii) (m2 − n2m)2 + 2m3n2 Answer:

(i) (a2 − b2)2 = (a2)2 − 2(a2) (b2) + (b2)2 [(a − b)2 = a2 − 2ab + b2 ]

= a4 − 2a2b2 + b4

(ii) (2x +5)2 − (2x − 5)2 = (2x)2 + 2(2x) (5) + (5)2 − [(2x)2− 2(2x) (5) + (5)2]

[(a − b)2 = a2 − 2ab + b2]

[(a + b)2 = a2 + 2ab + b2]

= 4x2 + 20x + 25 − [4x2 − 20x + 25]

= 4x2 + 20x + 25 − 4x2 + 20x − 25 = 40x

(iii) (7m − 8n)2 + (7m + 8n)2

= (7m)2 − 2(7m) (8n) + (8n)2 + (7m)2 + 2(7m) (8n) + (8n)2

[(a − b)2 = a2 − 2ab + b2and (a + b)2 = a2 + 2ab + b2]

= 49m2 − 112mn + 64n2 + 49m2 + 112mn + 64n2

= 98m2 + 128n2

(iv) (4m + 5n)2 + (5m + 4n)2

= (4m)2 + 2(4m) (5n) + (5n)2 + (5m)2 + 2(5m) (4n) + (4n)2

[ (a + b)2 = a2 + 2ab + b2]

= 16m2 + 40mn + 25n2 + 25m2 + 40mn + 16n2

= 41m2 + 80mn + 41n2

(v) (2.5p − 1.5q)2 − (1.5p − 2.5q)2

= (2.5p)2 − 2(2.5p) (1.5q) + (1.5q)2 − [(1.5p)2 − 2(1.5p)(2.5q) + (2.5q)2]

[(a − b)2 = a2 − 2ab + b2 ]

= 6.25p2 − 7.5pq + 2.25q2 − [2.25p2 − 7.5pq + 6.25q2]

= 6.25p2 − 7.5pq + 2.25q2 − 2.25p2 + 7.5pq − 6.25q2]

= 4p2 − 4q2

(vi) (ab + bc)2 − 2ab2c

= (ab)2 + 2(ab)(bc) + (bc)2 − 2ab2c [(a + b)2 = a2 + 2ab + b2 ]

= a2b2 + 2ab2c + b2c2 − 2ab2c

= a2b2 + b2c2

(vii) (m2 − n2m)2 + 2m3n2

= (m2)2 − 2(m2) (n2m) + (n2m)2 + 2m3n2 [(a − b)2 = a2 − 2ab + b2 ]

= m4 − 2m3n2 + n4m2 + 2m3n2 = m4 +

n4m2Question 5:

Show that

(i) (3x + 7)2 − 84x = (3x − 7)2 (ii) (9p − 5q)2 + 180pq = (9p + 5q)2

(iii)

(iv) (4pq + 3q)2− (4pq − 3q)2 = 48pq2

(v) (a − b) (a + b) + (b − c) (b + c) + (c − a) (c + a) = 0 Answer:

(i) L.H.S = (3x + 7)2 − 84x

= (3x)2 + 2(3x)(7) + (7)2 − 84x

= 9x2 + 42x + 49 − 84x

= 9x2 − 42x + 49

R.H.S = (3x − 7)2 = (3x)2 − 2(3x)(7) +(7)2

= 9x2− 42x + 49

L.H.S = R.H.S

(ii) L.H.S = (9p − 5q)2 + 180pq

= (9p)2 − 2(9p)(5q) + (5q)2 − 180pq

= 81p2 − 90pq + 25q2 + 180pq

= 81p2 + 90pq + 25q2

R.H.S = (9p + 5q)2

= (9p)2 + 2(9p)(5q) + (5q)2

= 81p2 + 90pq + 25q2

L.H.S = R.H.S

(iv) L.H.S = (4pq + 3q)2− (4pq − 3q)2

= (4pq)2 + 2(4pq)(3q) + (3q)2 − [(4pq)2 − 2(4pq) (3q) + (3q)2]

= 16p2q2 + 24pq2 + 9q2 − [16p2q2 − 24pq2 + 9q2]

= 16p2q2 + 24pq2 + 9q2 −16p2q2 + 24pq2 − 9q2

= 48pq2 = R.H.S

(v) L.H.S = (a − b) (a + b) + (b − c) (b + c) + (c − a) (c + a) = (a2 − b2) + (b2 − c2) +

(c2 − a2) = 0 = R.H.S.

Question 6:

Using identities, evaluate.

(i) 712 (ii) 992 (iii) 1022 (iv) 9982

(v) (5.2)2 (vi) 297 × 303 (vii) 78 × 82

(viii) 8.92 (ix) 1.05 × 9.5

Answer:

(i) 712 = (70 + 1)2

= (70)2 + 2(70) (1) + (1)2 [(a + b)2 = a2 + 2ab + b2 ]

= 4900 + 140 + 1 = 5041

(ii) 992 = (100 − 1)2

= (100)2 − 2(100) (1) + (1)2 [(a − b)2 = a2 − 2ab + b2 ]

= 10000 − 200 + 1 = 9801

(iii) 1022 = (100 + 2)2

= (100)2 + 2(100)(2) + (2)2 [(a + b)2 = a2 + 2ab + b2 ]

= 10000 + 400 + 4 = 10404

(iv) 9982 = (1000 − 2)2

= (1000)2 − 2(1000)(2) + (2)2 [(a − b)2 = a2 − 2ab + b2 ]

= 1000000 − 4000 + 4 = 996004

(v) (5.2)2 = (5.0 + 0.2)2

(iii) L.H.S =

= (5.0)2 + 2(5.0) (0.2) + (0.2)2 [(a + b)2 = a2 + 2ab + b2 ]

= 25 + 2 + 0.04 = 27.04

(vi) 297 × 303 = (300 − 3) × (300 + 3)

= (300)2 − (3)2 [(a + b) (a − b) = a2 − b2]

= 90000 − 9 = 89991

(vii) 78 × 82 = (80 − 2) (80 + 2)

= (80)2 − (2)2 [(a + b) (a − b) = a2 − b2]

= 6400 − 4 = 6396

(viii) 8.92 = (9.0 − 0.1)2

= (9.0)2 − 2(9.0) (0.1) + (0.1)2 [(a − b)2 = a2 − 2ab + b2 ]

= 81 − 1.8 + 0.01 = 79.21

(ix) 1.05 × 9.5 = 1.05 × 0.95 × 10

= (1 + 0.05) (1− 0.05) ×10

= [(1)2 − (0.05)2] × 10

= [1 − 0.0025] × 10 [(a + b) (a − b) = a2 − b2]

= 0.9975 × 10 = 9.975

Question 7:

Using a2−b2 = (a + b) (a − b), find

(i) 512 − 492 (ii) (1.02)2 − (0.98)2 (iii) 1532 − 1472

(iv) 12.12 − 7.92 Answer:

(i) 512 − 492 = (51 + 49) (51 − 49)

= (100) (2) = 200

(ii) (1.02)2 − (0.98)2 = (1.02 + 0.98) (1.02 − 0.98)

= (2) (0.04) = 0.08

(iii) 1532 − 1472 = (153 + 147) (153 − 147)

= (300) (6) = 1800

(iv) 12.12 − 7.92 = (12.1 + 7.9) (12.1 − 7.9)

= (20.0) (4.2) = 84 Question 8:

Using (x + a) (x + b) = x2 + (a + b) x + ab, find (i) 103 × 104 (ii) 5.1

× 5.2 (iii) 103 × 98 (iv) 9.7 × 9.8 Answer:

(i) 103 × 104 = (100 + 3) (100 + 4)

= (100)2 + (3 + 4) (100) + (3) (4)

= 10000 + 700 + 12 = 10712

(ii) 5.1 × 5.2 = (5 + 0.1) (5 + 0.2)

= (5)2 + (0.1 + 0.2) (5) + (0.1) (0.2)

= 25 + 1.5 + 0.02 = 26.52

(iii) 103 × 98 = (100 + 3) (100 − 2)

= (100)2 + [3 + (− 2)] (100) + (3) (− 2)

= 10000 + 100 − 6

= 10094

(iv) 9.7 × 9.8 = (10 − 0.3) (10 − 0.2)

= (10)2 + [(− 0.3) + (− 0.2)] (10) + (− 0.3) (− 0.2)

= 100 + (− 0.5)10 + 0.06 = 100.06 − 5 = 95.06


Following are the car parking charges near a railway station up to

4 hours Rs 60

8 hours Rs 100

12 hours Rs 140

24 hours Rs 180

Check if the parking charges are in direct proportion to the parking time.

Answer:

A table of the given information is formed as

Number of

hours

4 8 12 24

Parking

charges

(in Rs)

60 100 140 180

The ratio of parking charges to the respective number of hours (Rs/ hour) can be calculated

as

As each ratio is not same, therefore, the parking charges are not in a direct proportion to

the parking time.

Question 2:

A mixture of paint is prepared by mixing 1 part of red pigments with 8 parts of base.

In the following table, find the parts of base that need to be added.

Parts of

red

pigment

1 4 7 12 20

parts of

base

8 … … … …

Answer:

The given mixture of paint is prepared by mixing 1 part of red pigments with 8 parts of

base. For more parts of red pigments, the parts of the base will also be more.

Therefore, the parts of red pigments and the parts of base are in direct proportion.

The given information in the form of a table is as follows.

Parts of

red

pigment

1 4 7 12 20

Parts of base 8x1 x2 x3 x4

According to direct proportion,

The table can be drawn as follows.

Parts of

red

pigment

1 4 7 12 20

Parts of base 8 32 56 96 160

Question 3:

In Question 2 above, if 1 part of a red pigment requires 75 mL of base, how much red

pigment should we mix with 1800 mL of base?

Answer:

Let the parts of red pigment required to mix with 1800 mL of base be x.


Parts of

red

pigment

1 x

Parts of

base (in

mL)

75 1800

The parts of red pigment and the parts of base are in direct proportion.

Therefore, we obtain

Thus, 24 parts of red pigments should be mixed with 1800 mL of base.

Question 4:

A machine in a soft drink factory fills 840 bottles in six hours. How many bottles will it fill in

five hours?

Answer:

Let the number of bottles filled by the machine in five hours be x.


Number of

bottles

840 X

Time

taken

(in

hours)

6 5

The number of bottles and the time taken to fill these bottles are in direct proportion.


Thus, 700 bottles will be filled in 5 hours.

Question 5:

A photograph of a bacteria enlarged 50,000 times attains a length of 5 cm. What is the

actual length of the bacteria? If the photograph is enlarged 20,000 times only, what would

be its enlarged length?

Answer:

Let the actual length of bacteria be x cm and the enlarged length of bacteria be y cm, if the

photograph is enlarged for 20,000 times.


Length of bacteria (in cm) 5 x y

Number of times photograph

of Bacteria was enlarged

50000 1 20000

The number of times the photograph of bacteria was enlarged and the length of bacteria are

in direct proportion.


Hence, the actual length of bacteria is 10−4 cm.

Let the length of bacteria when the photograph of bacteria is enlarged 20, 000 times be y.

Hence, the enlarged length of bacteria is 2 cm.

Question 6:

In a model of a ship, the mast is 9 cm high, while the mast of the actual ship is 12 m high.

If the length of the ship is 28 m, how long is the model ship?

Answer:

Let the length of the mast of the model ship be x cm.

The given information in the form of a table is as follows:

- Height

of

mast

Length

of ship

Model

ship

9 cm x

Actual

ship

12 m 28 m

We know that the dimensions of the actual ship and the model ship are directly proportional

to each other.

Therefore, we obtain:

Thus, the length of the model ship is 21 cm.

Question 7:

Suppose 2 kg of sugar contains 9 × 106 crystals.

How many sugar crystals are there in (i) 5 kg of sugar? (ii) 1.2 kg of sugar?

Answer:

(i) Let the number of sugar crystals in 5 kg of sugar be x.


Amount

of

sugar

(in kg)

2 5

Number of

crystals

9

×

106

x

The amount of sugar and the number of crystals it contains are directly proportional to each

other. Therefore, we obtain

Hence, the number of sugar crystals is 2.25 × 107.

(ii)Let the number of sugar crystals in 1.2 kg of sugar be y. The given information in the form of a

table is as follows.

Amount

of

sugar

(in kg)

2 1.2

Number of

crystals

9

×

106

y

Hence, the number of sugar crystals is .

Question 8:

Rashmi has a road map with a scale of 1 cm representing 18 km. She drives on a road for

72 km. What would be her distance covered in the map?

Answer:

Let the distance represented on the map be x cm.


Distance

covered on road

in (in km)

18 72

Distance

represented on

map (in cm)

1 x

The distances covered on road and represented on map are directly proportional to each


Hence, the distance represented on the map is 4 cm.

Question 9:

A 5 m 60 cm high vertical pole casts a shadow 3 m 20 cm long. Find at the same time −

(i) the length of the shadow cast by another pole 10 m 50 cm high (ii) the height of a

pole which casts a shadow 5 m long.

Answer:

(i) Let the length of the shadow of the other pole be x m.

1 m = 100 cm


Height of pole

(in m)

5.60 10.50

Length

of

shadow

(in m)

3.20 x

More the height of an object, more will be the length of its shadow.

Thus, the height of an object and length of its shadow are directly proportional to each


Hence, the length of the shadow will be 6 m.

(ii) Let the height of the pole be y m.


Height of pole

(in m)

5.60 y

Length

of

shadow

(in m)

3.20 5

The height of the pole and the length of the shadow are directly proportional to each other.

Therefore,

Thus, the height of the pole is 8.75 m or 8 m 75 cm.

Question 10:

A loaded truck travels 14 km in 25 minutes. If the speed remains the same, how far can it

travel in 5 hours?

Answer:

Let the distance travelled by the truck in 5 hours be x km.

We know, 1 hour = 60 minutes

∴5 hours = (5 × 60) minutes = 300 minutes


Distance

travelled

(in km)

14 x

Time (in min) 25 300

The distance travelled by the truck and the time taken by the truck are directly proportional

to each other. Therefore,

Hence, the distance travelled by the truck is 168 km.


Which of the following are in inverse proportion?

(i) The number of workers on a job and the time to complete the job.

(ii) The time taken for a journey and the distance travelled in a uniform speed.

(iii) Area of cultivated land and the crop harvested.

(iv) The time taken for a fixed journey and the speed of the vehicle.

(v) The population of a country and the area of land per person.

Answer:

(i) These are in inverse proportion because if there are more workers, then it will take lesser

time to complete that job.

(ii) No, these are not in inverse proportion because in more time, we may cover more distance

with a uniform speed.

(iii) No, these are not in inverse proportion because in more area, more quantity of crop may be

harvested.

(iv) These are in inverse proportion because with more speed, we may complete a certain

distance in a lesser time.

(v) These are in inverse proportion because if the population is increasing, then the area of the

land per person will be decreasing accordingly.

Question 2:

In a Television game show, the prize money of Rs 1,00,000 is to be divided equally

amongst the winners. Complete the following table and find whether the prize money given

to an individual winner is directly or inversely proportional to the number of winners?

Numb

er of

winne

rs

1 2 4 5 8 1

0

2

0

Prize

for

each

winne

r (in

Rs)

1000

00

500

00

… … … … …

Answer:

A table of the given information is as follows.

Numb

er of

winne

rs

1 2 4 5 8 1

0

2

0

Prize

for

each

winne

r (in

Rs)

1000

00

500

00

x

1

x

2

x

3

x

4

x

5

From the table, we obtain

1 × 100000 = 2 × 50000 = 100000

Thus, the number of winners and the amount given to each winner are inversely

proportional to each other. Therefore,

1 × 100000 = 4 × x1

1 × 100000 = 5 × x2

1 × 100000 = 8 × x3

1 × 100000 = 10 × x4

1 × 100000 = 20 × x5

Question 3:

Rehman is making a wheel using spokes. He wants to fix equal spokes in such a way that

the angles between any pair of consecutive spokes are equal. Help him by completing the

following table.

Number of

spokes

4 6 8 10 12

Angle

between a

pair of

consecutive

spokes

90° 60° … … …

(i) Are the number of spokes and the angles formed between the pairs of consecutive spokes in

inverse proportion?

(ii) Calculate the angle between a pair of consecutive spokes on a wheel with 15 spokes.

(iii) How many spokes would be needed, if the angle between a pair of consecutive spokes is

40°?

Answer:

A table of the given information is as follows.

Number of

spokes

4 6 8 10 12

Angle

between a

pair of

consecutive

spokes

90° 60°

x1 x2 x3

From the given table, we obtain

4 × 90° = 360° = 6 × 60°

Thus, the number of spokes and the angle between a pair of consecutive spokes are

inversely proportional to each other. Therefore,

4 × 90° = x1 × 8

Thus, the following table is obtained.

Number of

spokes

4 6 8 10 12

Simi

larly

a

n

Angle

between a

pair of

consecutive

spokes

90° 60° 45° 36° 30°

(i) Yes, the number of spokes and the angles formed between the pairs of consecutive

spokes are in inverse proportion.

(ii)Let the angle between a pair of consecutive spokes on a wheel with 15 spokes be x. Therefore, 4

× 90° = 15 × x

Hence, the angle between a pair of consecutive spokes of a wheel, which has 15 spokes in

it, is 24°.

(iii) Let the number of spokes in a wheel, which has 40º angles between a pair of

consecutive spokes, be y.

Therefore,

4 × 90° = y × 40°

Hence, the number of spokes in such a wheel is 9.

Question 4:

If a box of sweets is divided among 24 children, they will get 5 sweets each. How many

would each get, if the number of the children is reduced by 4?

Answer:

Number of remaining children = 24 − 4 = 20

Let the number of sweets which each of the 20 students will get, be x.

The following table is obtained.

Number

of

students

24 20

Number

of

sweets

5 x

If the number of students is lesser, then each student will get more number of sweets.

Since this is a case of inverse proportion,

24 × 5 = 20 × x

Hence, each student will get 6 sweets.

Question 5:

A farmer has enough food to feed 20 animals in his cattle for 6 days. How long would the

food last if there were 10 more animals in his cattle?

Answer:

Let the number of days that the food will last if there were 10 more animals in the cattle be

x. The following table is obtained.

Number

of

animals

20 20

+

10

=

30

Number

of days

6 x

More the number of animals, lesser will be the number of days for which the food will last.

Hence, the number of days the food will last and the number of animals are inversely

proportional to each other.

Therefore,

20 × 6 = 30 × x

Thus, the food will last for 4 days.

Question 6:

A contractor estimates that 3 persons could rewire Jasminder’s house in 4 days. If, he uses

4 persons instead of three, how long should they take to complete the job?

Answer:

Let the number of days required by 4 persons to complete the job be x.


Number

of days

4 x

Number

of

persons

3 4

If the number of persons is more, then it will take lesser time to complete the job. Hence,

the number of days and the number of persons required to complete the job are inversely


Therefore,

4 × 3 = x × 4

Thus, the number of days required to complete the job is 3.

Question 7:

A batch of bottles was packed in 25 boxes with 12 bottles in each box. If the same batch is

packed using 20 bottles in each box, how many boxes would be filled?

Answer:

Let the number of boxes filled, by using 20 bottles in each box, be x.


Number

of

bottles

12 20

Number

of

boxes

25 x

More the number of bottles, lesser will be the number of boxes.

Hence, the number of bottles and the number of boxes required to pack these are inversely


Therefore,

12 × 25 = 20× x

Hence, the number of boxes required to pack these bottles is 15.

Question 8:

A factory required 42 machines to produce a given number of articles in 63 days. How many

machines would be required to produce the same number of articles in 54 days? Answer:

Let the number of machines required to produce articles in 54 days be x. The following table

is obtained.

Number

of

machines

42 x

Number

of days

63 54

More the number of machines, lesser will be the number of days that it will take to produce

the given number of articles. Thus, this is a case of inverse proportion.

Therefore,

42 × 63 = 54× x

Hence, the required number of machines to produce the given number of articles in 54 days

is 49.

Question 9:

A car takes 2 hours to reach a destination by travelling at the speed of 60 km/h. how long

will it take when the car travels at the speed of 80 km/h?

Answer:

Let the time taken by the car to reach the destination, while travelling with a speed of 80

km/hr, be x hours.


Speed

(in

km/hr)

60 80

Time

taken

(in

hours)

2 x

More the speed of the car, lesser will be the time taken by it to reach the destination.

Hence, the speed of the car and the time taken by the car are inversely proportional to each

other. Therefore, 60 × 2 = 80× x

The time required by the car to reach the given destination is hours.

Question 10:

Two persons could fit new windows in house in 3 days.

(i) One of the persons fell ill before the work started. How long would the job take now?

(ii) How many persons would be needed to fit the windows in one day?

Answer:

(i) Let the number of days required by 1 man to fit all the windows be x. The following

table is obtained.

Number

of

persons

2 1

Number

of days

3 x

Lesser the number of persons, more will be the number of days required to fit all the

windows. Hence, this is a case of inverse proportion. Therefore,

2 × 3 = 1× xx = 6

Hence, the number of days taken by 1 man to fit all the windows is 6.

(ii) Let the number of persons required to fit all the windows in one day be y. The following

table is formed.

Number

of

persons

2 Y

Number

of days

3 1

Lesser the number of days, more will be the number of persons required to fit all the

windows. Hence, this is a case of inverse proportion. Therefore,

2 × 3 = y × 1 y = 6

Hence, 6 persons are required to fit all the windows in one day.

Question 11:

A school has 8 periods a day each of 45 minutes duration. How long would each period be,

if the school has 9 periods a day, assuming the number of school hours to be the same?

Answer:

Let the duration of each period, when there are 9 periods a day in the school, be x minutes.


Duration of each

period (in

minutes)

45 x

Number of

periods

8 9

If there is more number of periods a day in the school, then the duration of each period will

be lesser. Hence, this is a case of inverse proportion. Therefore

45 × 8 = x× 9

Hence, in this case, the duration of each period will be 40 minutes.


Evaluate

(i) 3−2 (ii) (−4)−2 (iii) Answer:

(i)

(ii)

(iii)

Question 2:

Simplify and express the result in power notation with positive

exponent.

(i)

(iii)

(v)

Answer:

(i) (−4)5 ÷ (−4)8 = (−4)5 − 8 (am ÷ an = am − n)

= (− 4)−3

(ii)

(iii)

(ii)

(iv)

(iv) (3− 7 ÷ 3−10) × 3−5 = (3−7 − (−10)) × 3−5 (am ÷ an = am −n)

= 33 × 3−5

= 33 + (− 5) (am × an = am + n)

= 3−2

Question 3:

Find the value of.

(i) (30 + 4−1) × 22 (ii) (2−1 × 4−1) ÷2−2

(iii) (iv) (3−1 + 4−1 + 5−1)0

(v)

Answer:

(ii) (2−1 × 4−1) ÷ 2− 2 = [2−1 × {(2)2}− 1] ÷ 2− 2

= (2− 1 × 2− 2) ÷ 2− 2

= 2−1+ (−2) ÷ 2−2 (am × an = am + n)

= 2−3 ÷ 2−2

= 2−3− (−2) (am ÷ an = am − n)

= 2−3 + 2 = 2 −1

(i)

(v) 2−3 × (−7)−3 =

(iv) (3 + 4 + 5 )

= 1 (a0 = 1)

(v)

Question 4:

Evaluate (i)

Answer:

Question 5:

Find the value of m for which 5m ÷5−3 = 55.

Answer:

5m ÷ 5−3 = 55

5m− (− 3) = 55 (am ÷ an = am − n)

5m + 3 = 55

(i)

(ii)

(ii)

(iii)

−1 −1 −1 0

Since the powers have same bases on both sides, their respective exponents must be equal. m + 3

= 5 m = 5 − 3 m = 2

Question 6:

Evaluate (i)

Answer:

Question 7:

Simplify. (i)

Answer:

(i)

(ii)

(i)

(ii)

(ii)


Express the following numbers in standard form.

(i) 0.0000000000085 (ii) 0.00000000000942

(iii) 6020000000000000 (iv) 0.00000000837

(v) 31860000000 Answer:

(i) 0.0000000000085 = 8.5 × 10−12

(ii)0.00000000000942 = 9.42 × 10−12 (iii) 6020000000000000 = 6.02 × 1015

(iv) 0.00000000837 = 8.37 × 10−9

(v) 31860000000 = 3.186 × 1010

Question 2:

Express the following numbers in usual form.

(i) 3.02 × 10−6 (ii) 4.5 × 104

(iii) 3 × 10−8 (iv) 1.0001 × 109 (v) 5.8 × 1012 (vi)

3.61492 × 106 Answer:

(i) 3.02 × 10−6 = 0.00000302

(ii)

(ii) 4.5 × 104 = 45000

(iii) 3 × 10−8 = 0.00000003

(iv) 1.0001 × 109 = 1000100000

(v) 5.8 × 1012 = 5800000000000

(vi) 3.61492 × 106 = 3614920

Question 3:

Express the number appearing in the following statements in standard form.

(i) 1 micron is equal to m.

(ii) Charge of an electron is 0.000, 000, 000, 000, 000, 000, 16 coulomb.

(iii) Size of a bacteria is 0.0000005 m

(iv) Size of a plant cell is 0.00001275 m (v) Thickness of a thick paper is 0.07 mm Answer:

(i) = 1 × 10−6

(ii) 0.000, 000, 000, 000, 000, 000, 16 = 1.6 × 10−19

(iii) 0.0000005 = 5 × 10−7

(iv) 0.00001275 = 1.275 × 10−5

(v) 0.07 = 7 × 10−2Question 4:

In a stack there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016

mm. What is the total thickness of the stack?

Answer:

Thickness of each book = 20 mm

Hence, thickness of 5 books = (5 × 20) mm = 100 mm

Thickness of each paper sheet = 0.016 mm

Hence, thickness of 5 paper sheets = (5 × 0.016) mm = 0.080 mm

Total thickness of the stack = Thickness of 5 books + Thickness of 5 paper sheets

= (100 + 0.080) mm

= 100.08 mm

= 1.0008 × 102 mm

On Book

1

On Book

(Frame)

2

Qno.4 , 5 and 6 on Page No: 03,04,05

On Book

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Do Your self

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On Book

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On Book

On Book

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(Biodegridiable Act 2007)

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Do your self

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(Compound) (Simple)

2

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(Preposition)

(Conjuction)

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O3

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Common Noun

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Proper Noun

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Common Noun

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Proper Noun

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