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Wonderful world of Decimals . What is a decimal number?. Think about money. A decimal is a part of a whole . 1 dollar and 4 dimes. 1.40$. Part of the whole. Whole . On a number line. 1. 4. 0. Converting from fraction to Decimal. THERE ARE 2 WAYS - PowerPoint PPT Presentation
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WONDERFUL WORLD OF DECIMALS
What is a decimal number?
A decimal is a part of a whole.
•Think about money
1 dollar and 4 dimes
•1.40$
Whole
Part of the whole
On a number line
1 4 0
Converting from fraction to Decimal• THERE ARE 2 WAYS• 1) You can write the fraction with a denominator that is a
power of 10.• (10,100,1000….)
Denominator is the bottom number of a fraction• Ex
• =
Step 2• Than move your decimal place one spot to the left, because the 10 has 1 zero.
• 6.
0 .6
More examples
How many decimal points will I move to the left?
245.
Look at money again.
•It takes 10 dimes to make 1 dollar.
So 1 dime is 1 tenth of the whole
It takes 100 pennies to make 1 dollar
A penny is one hundredth of a dollar
Second way
•Divide the numerator by the denominator.
• 7÷16• =0.4375
Express the following mixed fraction as a decimal
• 2 =2. a decimal•2÷3 =0.66•2.66
Homework• Pg 90#15,16,17
• Pg 91# 18,19,20
Comparing decimal numbers• If 2 decimal numbers have different wholes • Ex.• 4.56 and 7.89
• The one with the larger whole is bigger.
Comparing decimal numbers• If the 2 numbers have the same whole but different
decimal numbers.
• 6.54 and 6.43
• The one with the larger tenth digit is bigger
Adding and subtracting decimals• Example : 235.7 +18.276• 1) Write digits with the same position under each other
and line up the decimal point.• 235.7• + 18.276
• 2) Add or (subtract) the numbers ignoring the decimal point.
• 235.7• + 18.276
Adding and subtracting decimals• 3) Place the decimal point directly under the decimal of
the other numbers.• • 2 3 5 .7• + 1 8 .2 7 6
• 2 5 3. 976
Homework
Pg 94#1-5
Word Problem• You are going shopping for groceries and you want to
save as much money as possible. Here are the prices at 2 stores: Item Loblaws Super C
Milk 3.59$ a litre 3.55$ a litre
Bread 4.39$ 3.99$
Eggs 5.19$ for 12 4.39 $ for 12
Yogart 2.99$ for 2 3.45$ for 6
Which Grocery store would give you the best deal overall and how much would it cost?
Pg 95• #7-11
Multiplication and division of decimals• 1) When multiplying by a power of ten (10,100,1000…)
Move the decimal one place to the right for every zero
Example: 3.45 X100 3.45 =345.00
Multplication with decimal numbers
003.45 =.00345
Move the decimal one place to the Left for every zero.
Multiplication• For all other numbers,• 1) Multiply them as if they were not decimal numbers.
• 35.18• X 4.7• 24 626• + 1 40 720• 1 65 346• 2) Count the number of decimal places in the 2 numbers• we have 3.• 3) Put the decimal place in the result so it is same as the
total of the 2 numbers.
Homework• Pg 96• ALL• Pg 97 #3 & 4