Transcript Lesson 5.7

Lesson 5.7
Core Focus on Decimals
& Fractions
Multiplying and Dividing Mixed
Numbers
Warm-Up
1. Write 3 12 as an improper fraction.
7
2
2. Write
as an improper fraction.
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5
3. Write 2 79 as an improper fraction.
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4. Write 9 13 as an improper fraction.
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3
4 53
Lesson 5.7
Multiplying and Dividing
Mixed Numbers
Find products and quotients of
expressions that include mixed numbers.
Explore!
Scrapbooking
Katelyn enjoys putting her photos into scrapbooks. When she works diligently, she
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completes 3 2 pages each hour.
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Step 1 Katelyn’s relatives are coming in 2 2 hours. Katelyn wants to know how many
pages she can finish before they arrive.
a.
b.
c.
Write a math problem that will help her determine this.
Change each mixed number to an improper fraction and calculate.
Simplify the answer. Write it in a complete sentence.
Step 2 Katelyn plans to complete 14 pages of her scrapbook tomorrow. How many
hours will it take her?
a.
b.
c.
Write the problem.
Change both the whole number and mixed number to fractions
and calculate.
Simplify the answer. Write the answer in a complete sentence.
Explore!
Scrapbooking
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Step 3 Katelyn spent a total of 9 3 hours on her scrapbook last week.
How many pages did she complete?
Step 4 Stephen is just learning to scrapbook.
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He can finish 2 4 pages each hour. He
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worked with Katelyn for the entire 9 3
hours last week. How many pages did
he complete?
Step 5 Describe in words the steps to take when multiplying or dividing two mixed
numbers.
Multiplying and Dividing
Mixed Numbers
1. Write each mixed or whole number
as an improper fraction.
2. Multiply or divide using the
improper fractions.
3. Write the answer in simplest form.
Example 1
Find the value of 7 1  1 1 .
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4
Change each mixed number
to an improper fraction.
7 13 
22
3
Rewrite and multiply.
Write as a mixed number.
7 13  1 14  9 16
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 9 16
6
1
5
14  4
Example 2
Brennan brought 7 83 pounds of salmon for his family. Each
portion was about 12 pound of salmon. How many portions
could he serve?
Write the problem.
Write the mixed number as an
improper fraction.
Divide.
3
8
1
2
7 83 =
59
8
7 
59 1 59 2 59  2 118
   

 14 86
8 2 8 1 8 1
8
Simplify.
He can serve 14 43 portions of salmon.
14 86  14 34
Example 3
Isaac built a tree house for his daughter. He cut a board
into 5 equal pieces. How long is each piece of board if
the original board was 11 12 feet long?
Write the problem.
11 12  5
Write each whole and mixed
number as an improper fraction.
11 12
Multiply by the reciprocal
of the divisor.
Each equal piece of board is 2 103 feet long.
23
5

and 5 
2
1
23 5 23 1 23
   
 2 103
2 1 2 5 10
Communication Prompt
What clues do you look for when reading word
problems to figure out which operation (+, −, ×, ÷) you
will use?
Exit Problems
1. Find the value of 2 16  2 13 .
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2. Find the value of 4 14  1 34 .
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2
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3. Marlene can make 5 12 cards each hour. How many cards can
she make in 2 12 hours?
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13 cards
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4. Cory stacked 1 14 inch thick boards on top of each other.
When he finished stacking boards, the stack was 11 14 inches
high. How many boards did he stack?
9 boards