01/06/10 Divide Decimals#5. LT: I will divide decimals. Warm Up: 5×7 1×7 4 ×7. 9×7 7×10 7×8. 7×2 7×3 7×7. 7×6 7×100 7×11. Today’s Plan: -Multiplication Practice -Correct Homework -Divide Decimals. Learning Target:
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01/06/10 Divide Decimals#5
LT: I will divide decimals.
Today’s Plan:
-Multiplication Practice
-Correct Homework
-Divide Decimals
Learning Target:
-I will divide decimals.
01/06/10 Divide Decimals#5
LT: I will divide decimals.
Timed Test tomorrow 1-7
Today’s Plan:
-Multiplication Practice
-Correct Homework
-Divide Decimals
Learning Target:
-I will divide decimals.
01/06/10 Divide Decimals#5
LT: I will divide decimals.
Correct Homework
Today’s Plan:
-Multiplication Practice
-Correct Homework
-Divide Decimals
Learning Target:
-I will divide decimals.
Dividing Decimals and Integers by Decimals
4-5
Helpful Hint
Multiply both numbers by the least power of ten that will make the divisor an integer.
Course 2
Additional Example 1A: Dividing Decimals by Decimals
Divide.
A. 8.28 ÷ 4.6
Multiply both numbers by 10.
8.28 ÷ 4.6
= 82.8 ÷ 46
1.
8
)
82.8
46
Divide as with whole numbers.
46
–
8
36
–36 8
0
Dividing Decimals and Integers by Decimals
4-5
Course 2
Additional Example 1B: Dividing Decimals by Decimals
Divide.
B. 18.48 ÷ (–1.75)
18.48 ÷ (–1.75) =
1848 ÷ 175
Multiply both numbers by
100.
1
0
.5
6
Use zeros as placeholders
)
.
00
175
1848
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
Dividing Decimals and Integers by Decimals
4-5
Course 2
Insert Lesson Title Here
Try This: Example 1A
Divide.
A. 6.45 ÷ 0.5
6.45 ÷ 0.5
Multiply both numbers by10.
= 64.5 ÷ 5
1
2
9
.
)
5
Divide as with whole numbers.
64.5
5
–
14
–10
5
4
–4 5
0
Dividing Decimals and Integers by Decimals
4-5
Course 2
Try This: Example 1B
Divide.
B. 16.48 ÷ (–2.06)
Multiply both
numbers by 100.
1648 ÷ (206)
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.
Dividing Decimals and Integers by Decimals
4-5
Course 2
Additional Example 2A: Dividing Integers by Decimals
Divide. Estimate to check whether the answer is reasonable.
A. 4 ÷ 1.25
Multiply both numbers by 100.
400 ÷ 125
4.00 ÷ 1.25 =
.
3
2
)
125
Use zero as a placeholder.
400
.0
Divide as with whole numbers.
–375
25 0
–25 0
0
Estimate
The answer is reasonable.
4 ÷ 1 = 4
Dividing Decimals and Integers by Decimals
4-5
Course 2
Additional Example 2B:Dividing Integers by Decimals
Divide. Estimate to check whether the answer is Reasonable.
B. –24 ÷ (–2.5)
Multiply both numbers by 10.
–24.0 ÷ (–2.5) =
–240 ÷ (–25)
9
6
.
)
0
240
.
Divide as with whole numbers.
25
– 225
0
15
– 15 0
0
Estimate
–24 ÷ (–3) = 8
The answer is reasonable.
Dividing Decimals and Integers by Decimals
4-5
Course 2
Try This: Example 2A
Divide. Estimate to check whether the answer is reasonable.
A. 6 ÷ 1.25
Multiply both numbers by 100.
600 ÷ 125
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
Dividing Decimals and Integers by Decimals
4-5
Course 2
Try This: Example 2B
Divide. Estimate to check whether the answer is Reasonable.
B. –22 ÷ (–2.5)
Multiply both numbers by 10.
–22.0 ÷ (–2.5) =
–220 ÷ (–25)
8
8
.
)
0
220
.
Divide as with whole numbers.
25
–200
0
20
–20 0
0
Estimate
–22 ÷ (–3) = 7
The answer is reasonable.
4-4
Dividing Decimals by Integers
Course 2
Additional Example 2: Money Application
You can buy juice by the bottle or case. Either way, it costs the same for each bottle. A case of 24 bottles of juice cost $23.52. Kevin bought a bag of peanuts for 75¢ and one bottle of juice. How much did Kevin spend in all?
First find the cost for one bottle of juice by dividing the cost of a case by the number of bottles in a case. Then add the cost of a bag of peanuts.
0
.
9
8
)
24
Place the decimal point for the answer
directly above the decimal under the
division symbol.
23.52
21 6
1 92
–1 92
0
One bottle of juice costs $0.98
and a bag of peanuts costs $0.75
$0.98 + $0.75 = $1.73
Kevin spent a total of $1.73
4-4
Dividing Decimals by Integers
Course 2
Insert Lesson Title Here
Try This: Example 2
Cookies at a store sell for $1.80 a dozen. The cost for each cookie is the same whether you buy them individually or by the dozen. John decided to buy 1 cookie and a quart of milk. The milk cost $1.79. How much did John have to pay?
First find the cost of one cookie by dividing the cost of a dozen by 12. Then add the price for the milk.
0
.
1
5
)
12
Place the decimal point for the answer
directly above the decimal under the
division symbol.
1.80
1 2
60
– 60
0
One quart of milk costs
$1.79 and one cookie
costs $0.15.
$1.79 + $0.15 = $1.94
John spent a total of $1.94.
dividend÷divisor= quotient or quotient
divisor )dividend
7.2
36 ÷5= 7.2
)
5
36.0
– 35
10
– 10
0
01/06/10 Divide Decimals#5
LT: I will divide decimals.
Page 212 #1-6
Today’s Plan:
-Multiplication Practice
-Correct Homework
-Divide Decimals
Learning Target:
-I will divide decimals.