Transcript mgbmi2e_ppt_04_04

4.4
Dividing Decimals
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall.
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 Number
Step 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
Step 1: Place the decimal point in
the quotient directly above the
decimal point in the dividend.
Step 2: Divide as with whole
numbers.
Example
.
2 11.8
5.9
2 11.8
- 10
18
-18
0
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Example
Divide: 219.2÷8.
divisor
27.4
8 219.2
16
quotient
dividend
27.4
Check:
59

56
32
32
8
219.2
0
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Example
Divide: 0.6÷4.
divisor
0.15
4 0.60
4
20
20
quotient
dividend
0.15
Check:

4
0.60
0
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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.
2.46
2.8 6.888
becomes
28 68.88
56
128
112
168
168
0
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Estimating When Dividing Decimals
Divide 258.3 ÷ 2.8
Exact
92.25
28. 2583.
- 252
63
- 56
70
- 56
140
- 140
0
Estimate
rounds to
100
3 300
This is a reasonable answer.
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Estimating When Dividing Decimals
Example:
Divide: 0.54÷12. Then estimate to whether the
proposed result is reasonable.
Exact
0.045
12 0.540
48
60
60
0
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.
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Dividing Decimals by Powers of 10
There are patterns that occur when dividing by powers
of 10, such as 10, 100, 1000, and so on.
456.2
= 45 . 62
10
The decimal point moved 1 place
to the left.
1 zero
456.2
= 0 . 4562
1 , 000
The decimal point moved 3 places
to the left.
3 zeros
The pattern suggests the following rule.
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Example
Divide.
a. 548.6 = 0.5486
1000
b.
0.68
10
= 0.068
Move the decimal point 3 places to the left.
Move the decimal point 1 place to the left.
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