copyright © 2012 pearson education, inc. publishing as prentice hall. 4.4 dividing decimals
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Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall.
4.4
Dividing Decimals
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© 2012 Pearson Prentice Hall. All rights reserved
Dividing Decimals
Dividing decimal numbers is similar to dividing whole numbers. The only difference is that we place a decimal point in the quotient.
Dividing by a Whole NumberStep 1: Place the decimal point in the quotient directly above the decimal point in the dividend.Step 2: Divide as with whole numbers.
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Dividing Decimals
Dividing by a Whole Number Example
Step 1: Place the decimal point in the quotient directly above the decimal point in the dividend.
Step 2: Divide as with whole numbers.
.8.112
2 11.8
- 10
18
-18
0
5.9
44
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Example
Divide: 219.2÷8.
27.4 8 219.2
16
59
56
32
32
0
divisor dividend
quotient
Check: 27.4
8
219.2
55
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Example
Divide: 0.6÷4.
0.15 4 0.60
4
20
20
0
divisor dividend
quotient
Check: 0.15
4
0.60
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Dividing by a Decimals
If the divisor is not a whole number, before we divide we need to move the decimal point to the right until the divisor is a whole number.
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Example
Divide: 6.888÷2.8.
becomes 2.8 6.888 28 68.88
56
128
112
168
168
0
2.46
88
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Divide 258.3 ÷ 2.8Divide 258.3 ÷ 2.8
Estimating When Dividing Decimals
ExactExact EstimateEstimate
28. 2583. - 252 63 - 56 70 - 56 140 -140 0
rounds to 3 300100
This is a reasonable answer.
92.25
99
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Estimating When Dividing Decimals
Example:
Divide: 0.54÷12. Then estimate to whether the proposed result is reasonable.
0.045 12 0.540
48
60
60
0
Exact Estimate 0.05 10 0.50
50
0
The estimate is 0.05, so 0.045 is reasonable.
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Dividing by Powers
Dividing Decimals by Powers of 10 such as 10, 100 or 1000
Move the decimal point of the dividend to the left the same number of places there are zeros in the power of 10.
1111
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall.
There are patterns that occur when dividing by powers of 10, such as 10, 100, 1000, and so on.
The decimal point moved 1 place The decimal point moved 1 place to the left.to the left.
1 zero
3 zeros
The decimal point moved 3 places The decimal point moved 3 places to the left.to the left.
The pattern suggests the following rule.The pattern suggests the following rule.
.45 6210
456.2
1 0000 4562
,.456.2
Dividing Decimals by Powers of 10
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Example
Divide.
a.
b.
548.6
1000
0.68
10
= 0.5486 Move the decimal point 3 places to the left.
= 0.068 Move the decimal point 1 place to the left.