4-4 dividing decimals by integers course 2 warm up warm up problem of the day problem of the day...

4-4 Dividing Decimals by Integers

Course 2

Warm UpWarm Up

Problem of the DayProblem of the Day

Lesson PresentationLesson Presentation

Warm UpMultiply or divide.

8.84

31.25

8.954

55

63

Course 2

4-4 Dividing Decimals by Integers

1. 3.4 2.6

2. 6.25 5

3. 8.14 1.1

4. 825 ÷ 15

5. 756 ÷ 12

Problem of the Day

Divide 60 by and add 10. What is your

answer?

130

Course 2

4-4 Dividing Decimals by Integers

12

Learn to divide decimals by integers.

Course 2

4-4 Dividing Decimals by Integers

Elena received scores of 6.85, 6.95, 7.2, 7.1, and 6.9 on the balance beam at a gymnastics meet. To find her average score, add her scores and then divide by 5.

6.85 + 6.95 + 7.2 + 7.1 + 6.9 = 35

35 ÷ 5 = 7

Elena’s average score was 7, or 7.0.

Notice that the sum of Elena’s scores is an integer. But what if the sum is not an integer? You can find the average score by dividing a decimal by a whole number.

Course 2

4-4 Dividing Decimals by Integers

Insert Lesson Title Here

Division can undo multiplication.

0.2 · 4 = 0.8 and

0.8 ÷ 4 = 0.2

Remember!

Course 2

4-4 Dividing Decimals by Integers

0.8 ÷ 4 0.8 divided into 4 equal groups

0.8 ÷ 4 = 0.2

The size of each group is the answer.Each group is 2 columns, or 0.2.

Divide. Estimate to check whether the answer is reasonable.

Additional Example 1A: Dividing Decimals by Integers

A. 36.75 ÷ 7

)5

–351

–143

–3 50

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

Divide as with whole numbers.

Estimate35 ÷ 7 = 5 5.25 is a reasonable answer.

36.757.

7

2

5

5

Course 2

4-4 Dividing Decimals by Integers

Divide. Estimate to check whether the answer is reasonable.

Additional Example 1B: Dividing Decimals by Integers

B. 0.87 ÷ 3

)0

–627

–270

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

Divide as with whole numbers.

Estimate0.9 ÷ 3 = 0.3 0.29 is a reasonable answer.

0.873 .29

Course 2

4-4 Dividing Decimals by Integers

Course 2

4-4 Dividing Decimals by Integers

When you divide two numbers with different signs, the answer is negative.

Remember!

Divide. Estimate to check whether the answer is reasonable.

Additional Example 1C: Dividing Decimals by Integers

C. 82.08 ÷ (–27)

)3

–811–01

–1080

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

Estimate90 ÷ –30 = –3 The answer is reasonable.

.

0

08

Course 2

4-4 Dividing Decimals by Integers

82.08 ÷ (–27) = –3.04

The signs are different.

Think: 82.08 ÷ 27. 27 82.08

04

Try This: Example 1A

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Course 2

4-4 Dividing Decimals by Integers

Divide. Estimate to check whether the answer is reasonable.

A. 39.16 ÷ 4

)9

–363

–283

–3 60

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

Divide as with whole numbers.

Estimate9.79 is a reasonable answer.

39.164.

1

7

6

9

40 ÷ 4 = 10

Try This: Example 1B

Insert Lesson Title Here

Course 2

4-4 Dividing Decimals by Integers

Divide. Estimate to check whether the answer is reasonable.

B. 0.56 ÷ 4

)0

–416

–160

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

Divide as with whole numbers.

Estimate0.6 ÷ 4 = 0.15 0.14 is a reasonable answer.

0.564 .14

Try This: Example 1C

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Course 2

4-4 Dividing Decimals by Integers

Divide. Estimate to check whether the answer is reasonable.

C. 65.16 ÷ (–12)

)5

–605

–4 8

–360

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

Estimate

The answer is reasonable.

.

1

36

65.16 ÷ (–12) = –5.43

The signs are different.

Think: 65.16 ÷ 12 12 65.16

43

60 ÷ –12 = –5

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

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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 costs $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.

Lesson QuizDivide. Estimate to check whether each answer is reasonable.

1. 15.5 ÷ 5

2. 22.8 ÷ (–6)

3. 72.48 ÷ 24

4. 8.4 ÷ 12

5. Allison swam 5 sprint laps in the pool. If her times were 17.5, 19.3, 20.6, 17.4, and 16.7 seconds per lap, what was her average lap time?

–3.8

3.1

Insert Lesson Title Here

3.02

0.7

Course 2

4-4 Dividing Decimals by Integers

18.3 s