3-11 Dividing Fractions and Mixed Numbers Course 2 Warm Up Warm Up Problem of the Day Problem of the...

3-11 Dividing Fractions and Mixed Numbers

Course 2

Warm UpWarm Up

Problem of the DayProblem of the Day

Lesson PresentationLesson Presentation

Warm UpMultiply.

Course 2


1. 7 9

· 36

2. 98

· 65

3. 15

2 ·7

4. 212

· 114

7182720

720

or 1

2775 5

or 15

258 8

or 3 1

Problem of the Day

The Jeffers family is putting in a new fence around their yard. The yard is in the shape of a square. If they put nine fence posts on each side of the square, how many posts will be used?32

Course 2


Learn to divide fractions and mixed numbers.

Course 2


Vocabulary

reciprocal

Insert Lesson Title Here

Course 2


Course 2


When you divide 8 by 4 you find how many 4’s there are in 8. Similarly, when you divide

2 by , you find how many ’s there are in 2. 13

13

There are six ’s in 2. 13

Course 2


Reciprocals can help you divide by fractions. Two numbers are reciprocals if their product

is 1. The reciprocal of is 3 because 13

13

· 3= 13

· 31

= 33

= 1.

To divide by a fraction, find its reciprocal and thenmultiply.

2 ÷ 13

= 2 · 3 = 6

Additional Example 1: Dividing Fractions

Divide. Write each answer in simplest form.

A. 37 ÷ 2

537

÷ 25

= 37 ·

52

= 37

· 5· 2

=1514

or 1141

Multiply by the reciprocal of . 25

B. 38

÷ 12

38

÷ 12 =38

· 112

=38

· 112

1

4=

Multiply by the reciprocal of 12.

132

Course 2


Simplify.

Check It Out: Example 1


A. 35 ÷ 1

235

÷ 12

= 35 ·

21

= 35

· 2· 1

=65

or 151


B. 34

÷ 3

34

÷ 3 =34

· 13

=34

· 13

1

1=

Multiply by the reciprocal of 3.

14

Course 2


Simplify.



Course 2


A. 523

÷ 114

5 23

÷ 114

= 17 3

÷ 54

= 17 3

· 45

= 6815

or 4 815

Write mixed numbers as improperfractions.

Multiply by the reciprocal of 54

B. 34

÷ 212

34

÷ 2 12

= 34

÷ 52

= 34

· 25

=3 · 24 · 5

1

2= 3

10

Write 2 as an improper fraction.12


Simplify.

.

Additional Example 2: Dividing Mixed Numbers

Divide. Write the answer in simplest form.

Additional Example 2: Dividing Mixed Numbers

Course 2


C. 8 23

÷ 1327

8 23

÷ 1327

= 26 3

÷ 1327

= 26 3

· 2713

9

1

2

1

= 18 1

or 18



=26 3

· 2713·



Course 2


A. 323

÷ 112

3 23

÷ 112

= 11 3

÷ 32

= 11 3

· 23

= 22 9

or 2 4 9

Write mixed numbers as improperfractions.

Multiply by the reciprocal of 32

B. 35

÷ 125

35

÷ 1 25

= 35

÷ 75

= 35

· 57

=3 · 55 · 7

1

1= 3

7



Simplify.

.


Divide. Write the answer in simplest form.


Course 2


C. 7 15

÷ 18 5

7 15

÷ 18 5

= 36 5

÷ 18 5

= 36 5

· 5_18

1

1

2

1

= 21

or 2


Multiply by the reciprocal of . 18 5

= 36 5

· 518·

Additional Example 3: Social Studies Application

Course 2


The life span of a golden dollar coin is 30 years, while

paper currency lasts an average of 1 years. How many12

times longer will the golden dollar stay in circulation?

30 ÷ 1 12

= 30 1

÷ 32

Write the number as an improper fraction.

=30 1

· 23

Multiply by the reciprocal of .32

= ·Simplify.

30 21 3

10

1= 20

1or 20

The golden dollar will stay in circulation about20 times longer than paper currency.

·


Course 2


The average life of a queen ant is approximately 3 years.The life span of a worker ant is year. How many 3

7times longer will the queen ant live?

3 ÷ 37

= 31

÷37 Write the number as an improper fraction.

=31

· 73

Multiply by the reciprocal of .37

= · Simplify.3 71 3

1

1= 7

1or 7

The queen ant will live 7 times longer than the worker ant.

·

Lesson Quiz

10


Course 2



1.

2.

8 ÷ 45

59

÷ 18

3. 35

÷ 6

5. There are 5 14

yards of silk in a roll. If it takes 34

of a yard to make one designer scarf, how many scarves can be made from the roll?

7

4 49

40 9

or

110

34. 212

÷ 17

3544

3-11 Dividing Fractions and Mixed Numbers Course 2 Warm Up Warm Up Problem of the Day Problem of the...

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