Gene Maths 2

7/29/2019 Gene Maths 2

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Prof. M A ThiruthuvadossCell: 9445204774

for Excellence in Mathematics

http://www.magicmaths.org

REFORMMuch Needed

LongOverdueand

A Genuine

PutMATHSBACK

ONTRACK

Savethe Children&

MATHEMATICS!

Formula FactoryTamilnadu Std. VIII Text-Book


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Formula Factory (TAMILNADU STATE BOARD TEXT-BOOK STD VIII - 2011-12)

2

The 9-member (Text-Book) Committee ofTamilnadu

that prepared the above text-book has really done

A great service to the entire humanity.

They have successfully invented/identified 39 Rules and Formulae.

So that VIII Standard children may easily and instantly calculate

C.P., S.P., M.P., L.P.,

PROFIT/GAIN, LOSS, PROFIT/GAIN PERCENTAGE, LOSS PERCENTAGE,

SIMPLE INTEREST,

COMPOUND INTEREST FOR FRACTIONAL PERIODS LIKE 3 YEARS(INTEREST BEING COMPOUNDED HALF-YEARLY) ETC. ETC.

By Mugging up these 39 results

The children will get All the Life skills needed and live happily for the rest of their lives.

Sincere Congradulations for such a mighty contribution to Society & Mathemataics

Our ELDERS who were not that smart after all, used only 2 formulae namely

Simple interest =P n r

100

Compound Interest

Amount at the end of nth year is A = P

nr

1100


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3

Chapter 3: Life MathematicsPercentage, Application to Profit, Loss, Interest

3.1 Introduction3.2 Revision: Profit, Loss and Simple Interest Pages 95 - 96

RESULTS ON PROFIT, LOSS AND SIMPLE INTEREST

(i) Profit or Gain = Selling price Cost price

(ii) Loss = Cost price Selling price

(iii) Profit % =Profit

x 100

C.P.

(iv) Loss % =Loss

x 100C.P.

(v) Simple Interest (I) =Principal x Time x Rate

100=

Pnr

100

(vi) Amount = Principal + Interest

Example 3.5... ... ...

Remember

Percentage of increase =Increase in amount

x 100Original Amount

Percentage of decrease =Decrease in amount

x 100Original Amount


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4

3.3.2 Application of Profit and Loss Pages 99 - 100(i) Illustration of the formula for S.P.

Consider the ... ...

S.P. = C.P. + Profit

... ... ...

Selling price (S.P.) =(100 + Profit %)

x C.P.100

(ii) Illustration of the formula for S.P.

Consider the ... ...

We know S.P. = C.P. + Profit

... ... ...

C.P. =100

x S.P.(100 + Profit %)

We now summarize the formulae to calculate S.P. and C.P. as follows:

1. When there is profit 1. When there is a loss

(i) C.P. =100

x S.P.(100 + Profit %)

(i) C.P. =100

x S.P.(100 - Loss %)

2. When there is profit 2. When there is a loss

(ii) S.P. =(100 - Loss %)

x C.P.100

(ii) S.P. =(100 - Loss %)

x C.P.100


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3.3.4 Application of Discounts Pages 105-108

Discount is the reduction on the Marked Price orList Price of the article.

The normal pricr attached to the article before the discount

made is called as Marked Price (M.P.) or List Price of the article.

... ... ...

Hence we conclude the following:

Discount = Marked Price Selling Price

Selling Price = Marked Price Discount

Marked Price = Selling Price + Discount

Example 3.13[After a tedious solution, a formula-method is offered as a better option. - Prof. Doss]

M.P. =100

x S.P.(100 - Discount %)


M.P. =100 + Gain%

x C.P.(100 - Discount %)


C.P. =(100 - Discount %)

x M.P.100 + Gain%


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3.3.5 Application of Tax Pages 109-116

... ... ...

Calculation of Sales Tax

Amount of Sales Tax =Rate of Sales Tax

x Cost of the item100

Rate of Sales Tax =Amount of Sales Tax

x 100Cost of the item

Bill Amount = Cost of the item + Amount of Sales Tax

3.4 Compound Interest

... ... ...

Simple interest =P x n x r

100

Compound Interest

Amount at the end of nth year is A = P

nr

1100

C.I. at the end of n yeas is given by A P

(i.e.) C.I. = P

nr

1 100

P

To Compute Compound Interest

Case 1: Compunded Annually

Here A = P

nr

1100

and C.I. = A P


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Compound Interest Page 117

Case 2: Compunded Half-Yearly (Semi-Annually)

When the interest is compounded Half-Yearly, there are two conversion periods in a year each after 6 months. In such sitations, the

Half-Yearly rate will be half of the annual rate, that isr

2

.

In this case, A = P

2n

1 r1

2 100

and C.I. = A P

Case 3: Compunded QuarterlyWhen the interest is compounded quarterly, there are four conversion periods in a year and quarterly rate will be one-fourth of the

annual rate, r4

In this case, A = P

4n1 r

14 100

and C.I. = A P

Case 4: Compunded when time being fraction of a year

When interest is compounded annually but ime being a fraction.

In this case, when interest is compounded annually but time being a fraction of a year, say 51

4 years, ten amount A is given by

A = P

5r 1 r

1 1100 4 100

and C.I. = A P

for 5 years for 1

4year


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3.5 Difference between Simple Interest and Compound Interest Pages 120

When P is the Principal, n = 2 years and r is the Rate of interest,

Difference betweeen C.I. and S.I. for 2 years = P

2

r100

3.5.1 Appreciation and Depreciation

a) Appreciation A = P

nr

1100

b) Depreciation A = P

nr

1100

3.6 Fixed Deposits and Recurring Deposits

To find the formula for calculating interest and the maturity amount for R.D:

Let r% be the rate of interest paid and P be the monthly instalment paid for n monthsl

Interest =PNr

100, where N =

1 n(n 1)

12 2

years

Total Amount due at maturit is A = Pn +PNr

100

3.6.1 Hire Purchase and Instalments

Equated Monthly Instalmen (E.M.I.)

E.M.I. =Principal + Interest

Number of months

Example 3.5 ... ... ...

Monthly Instalment =Total amount

Number of months

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Gene Maths 2