01/06/10 Divide Decimals#5

01/06/10 Divide Decimals #5

Today’s Plan:-Multiplication Practice-Correct Homework-Divide Decimals

Learning Target: -I will divide decimals.

Warm Up:

1) 5×7

2) 1×7

3) 4×7

4) 9×7

5) 7×10

6) 7×8

7) 7×2

8) 7×3

9) 7×7

10) 7×6

11) 7×100

12) 7×11

LT: I will divide decimals.


Timed Test tomorrow 1-7





Correct Homework




Divide.

Additional Example 1A: Dividing Decimals by Decimals

8.28 ÷ 4.6

) 82.8461.

46–36 8

–36 8

Multiply both numbers by 10.

Divide as with whole numbers.

0

Multiply both numbers by the least power of ten that will make the divisor an integer.

Helpful Hint

A. 8.28 ÷ 4.6

8

= 82.8 ÷ 46

Course 2

4-5 Dividing Decimals and Integers by Decimals

Divide.

Additional Example 1B: Dividing Decimals by Decimals

B. 18.48 ÷ (–1.75)

18.48 ÷ (–1.75) = 1848 ÷ 175 Multiply both numbers by 100.

)175 1848 . 00 Use zeros as placeholdersDivide as with whole numbers.

1

–17598 0

0.5

–87 510 50

–10 50

0

18.48 ÷ (–1.75) = –10.56

6

The signs are different.

Course 2


Try This: Example 1A

Divide.

Insert Lesson Title Here

6.45 ÷ 0.5

) 64.5 51

5–14

–10

A. 6.45 ÷ 0.5

2

4 5

.9

–4 50

Multiply both numbers by10.


= 64.5 ÷ 5

Course 2


Divide.

B. 16.48 ÷ (–2.06)

16.48 ÷ (–2.06) = 1648 ÷ (206)

)1,6482068

–1 648

16.48 ÷ (–2.06) = –8

Multiply both numbers by 100.

Divide as with whole numbers.0

Try This: Example 1B

The signs are different.

Course 2


Divide. Estimate to check whether the answer is reasonable.

Additional Example 2A: Dividing Integers by Decimals

A. 4 ÷ 1.25

4.00 ÷ 1.25 = 400 ÷ 125 Multiply both numbers by 100.

)125 400 .0 Use zero as a placeholder.3

–37525 0

–25 0

0


Estimate4 ÷ 1 = 4 The answer is reasonable.

. 2

Course 2


Divide. Estimate to check whether the answer is Reasonable.

Additional Example 2B: Dividing Integers by Decimals

B. –24 ÷ (–2.5)

–24.0 ÷ (–2.5) = Multiply both numbers by 10.–240 ÷ (–25)

)25 2409

– 22515

.

.0

0

6

– 15 00

Estimate–24 ÷ (–3) = 8 The answer is reasonable.


Course 2


Divide. Estimate to check whether the answer is reasonable.

Try This: Example 2A

A. 6 ÷ 1.25

6.00 ÷ 1.25 = 600 ÷ 125 Multiply both numbers by 100.

)125 600 .0 Use zero as a placeholder.4

–500100 0

–100 00


Estimate6 ÷ 1 = 6 The answer is reasonable.

. 8

Course 2


Divide. Estimate to check whether the answer is Reasonable.

Try This: Example 2B

B. –22 ÷ (–2.5)

–22.0 ÷ (–2.5) = Multiply both numbers by 10.–220 ÷ (–25)

)25 2208

–20020

.

.0

0

8

–20 00

Estimate–22 ÷ (–3) = 7 The answer is reasonable.


Course 2


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?

Additional Example 2: Money Application

Course 2

4-4 Dividing Decimals by Integers

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)24 23.5221 61 92

–1 920

$0.98 + $0.75 = $1.73

Kevin spent a total of $1.73

.98Place the decimal point for the answerdirectly above the decimal under the division symbol.

One bottle of juice costs $0.98and a bag of peanuts costs $0.75

Try This: Example 2

Insert Lesson Title Here

Course 2

4-4 Dividing Decimals by Integers

0)12 1.801 2 60

– 600

$1.79 + $0.15 = $1.94

John spent a total of $1.94.

.15Place the decimal point for the answerdirectly above the decimal under the division symbol.

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.

One quart of milk costs$1.79 and one cookie costs $0.15.

Division Vocabulary

• The dividend is the number that is being divided. • The divisor is the number that the dividend will be divided by. • The quotient is the number of times the divisor will go into the

dividend. (The answer to the division problem.) dividend ÷ divisor = quotient or quotient

divisor )dividend

• In this example 5 is the divisor, 36 is the dividend, 7.2 is the quotient.

– 35)5 36.0

7.2

10 – 10

0

36 ÷ 5 = 7.2


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01/06/10 Divide Decimals#5