Warm Up

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Preview
Warm Up
California Standards
Lesson Presentation
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Warm Up Divide. 1. 24.5 7 2. 50.4 6 3. 19.2
(2) 4. 128.1 21
3.5
8.4
9.6
6.1
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When you divide two numbers, you can multiply
both numbers by the same power of ten
without changing the final answer.
Multiply both 0.6 and 0.3 by 10
0.6 ? 10 6
and
0.3 ? 10 3
and
6 3 2
0.6 0.3 2
By multiplying both numbers by the same power of
ten, you can make the divisor an integer.
Dividing by an integer is much easier than
dividing by a decimal.
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Additional Example 1B Dividing Decimals by
Decimals
Divide.
18.48 (1.75)
18.48 (1.75)
Multiply both numbers by 100 to make the divisor
an integer.
1
0
.5
6
Use zeros as placeholders.
)
.
175
1848
00
Divide as with whole numbers.
175
0
9
8
87 5
10 50
10 50
0
The signs are different.
18.48 (1.75) 10.56
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Additional Example 2A Dividing Integers by
Decimals
Divide. Estimate to check whether each answer is
reasonable.
4 1.25
4.00 1.25
Multiply both numbers by 100.
3
.
2
)
125
400
Use zero as a placeholder.
.0
375
Divide as with whole numbers.
25 0
25 0
0
Estimate
4 1 4
The answer is reasonable.
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Additional Example 2B Dividing Integers by
Decimals
Divide. Estimate to check whether each answer is
reasonable.
24 (2.5)
24.0 (2.5)
Multiply both numbers by 10.
9
.
6
)
240
.
0
Divide as with whole numbers.
25
225
15
0
15 0
0
Estimate
24 (3) 8
The answer is reasonable.
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Additional Example 3 Transportation Application
Eric paid 229.25 to rent a car. The fee to rent
the car was 32.75 per day. For how long did Eric
rent the car?
229.25 32.75
Multiply both numbers by 100.
7
)
22,925
3,275
Divide as with whole numbers.
22,925
0
Eric rented the car for 7 days.
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Check It Out! Example 1A
Divide.
6.45 0.5
6.45 0.5
Multiply both numbers by 10 to make the divisor
an integer.
1
2
9
.
)
5
Divide as with whole numbers.
64.5
5

14
10
4
5
4 5
0
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Check It Out! Example 2B
Divide. Estimate to check whether each answer is
Reasonable.
22 (2.5)
Multiply both numbers by 10.
22.0 (2.5)
8
8
.
)
220
0
25
.
Divide as with whole numbers.
200
20
0
20 0
0
Estimate
21 (3) 7
The answer is reasonable.
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Lesson Quiz
Divide. Estimate to check whether each answer is
reasonable. 1. 78.2 0.04 2. 9.72 2.7 3.
18.88 1.6 4. 19.5 3.25 5. Jordan used 32.46
gallons of gas to drive his van 584.28 miles.
How many miles did Jordan get per gallon?
1,995
3.6
11.8
6
18
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Check It Out! Example 1B
Divide.
16.48 (2.06)
Multiply both numbers by 100 to make the divisor
an integer.
16.48 (2.06)
8
)
206
1,648
1 648
Divide as with whole numbers.
0
16.48 (2.06) 8
The signs are different.
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Check It Out! Example 2A
Divide. Estimate to check whether each answer is
reasonable.
6 1.25
Multiply both numbers by 100.
6.00 1.25
4
.
8
)
125
Use zero as a placeholder.
600
.0
Divide as with whole numbers.
500
100 0
100 0
0
Estimate
The answer is reasonable.
6 1 6