Warm Up

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Warm Up
Problem of the Day
Lesson Presentation
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Warm Up 1. What is of 12? 2. What is of
100? 3. What is of 120? 4. What is of
100? 5. What is of 480?
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50
60
25
120
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Problem of the Day Your favorite uncle left
one-fifth of his estate to each of his three
children and the rest to his favorite charity. If
his estate was worth 105,000, how much was given
to charity?
42,000
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Learn to multiply fractions.
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On average, people spend of their lives
asleep. About of the time they sleep, they
dream. What fraction of a lifetime does a person
typically spend dreaming?
One way to find of is to make a
model. Find of .


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You can also multiply fractions without making a
model.
1 1
Multiply the numerators.
_____


Multiply the denominators.
4 3
The answer is in simplest form.

A person typically spends of his or her
lifetime dreaming.
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Additional Example 1A Multiplying
Fractions Multiply. Write each answer in simplest
form.

1 2
_____

Multiply numerators. Multiply denominators.

4 5
The GCF of 2 and 20 is 2.

The answer is in simplest form.

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Additional Example 1B Multiplying
Fractions Multiply. Write each answer in simplest
form.

Use the GCF to simplify the fractions before
multiplying. The greatest common factor of 5 and
15 is 5.
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3
1 4
_____
Multiply numerators. Multiply denominators.

7 3
The answer is in simplest form.

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Additional Example 1C Multiplying
Fractions Multiply. Write each answer in simplest
form.

4 6
______

Multiply numerators. Multiply denominators.

9 10
The GCF of 24 and 90 is 6.

The answer is in simplest form.

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Check It Out Example 1A Multiply. Write each
answer in simplest form.

1 3
_____

Multiply numerators. Multiply denominators.

2 6
The GCF of 3 and 12 is 3.

The answer is in simplest form.

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Check It Out Example 1B Multiply. Write each
answer in simplest form.

Use the GCF to simplify the fractions before
multiplying. The greatest common factor of 3 and
9 is 3.
1



3
1 5
_____
Multiply numerators. Multiply denominators.

7 3
The answer is in simplest form.

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Check It Out Example 1C Multiply. Write each
answer in simplest form.

3 5
______

Multiply numerators. Multiply denominators.

7 15
The GCF of 15 and 105 is 15.

The answer is in simplest form.

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Additional Example 2A Evaluating Fraction
Expressions
Evaluate the expression b for each value of
b. Write each answer in simplest form.
b
b
Substitute for b.

Multiply.
The answer is in simplest form.
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Additional Example 2B Evaluating Fraction
Expressions b
b
Substitute for b.

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Use the GCF to simplify.

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Multiply.
The answer is in simplest form.
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Additional Example 2C Evaluating Fraction
Expressions b
b

Substitute for b.
Multiply.
The GCF of 10 and 35 is 5.
The answer is in simplest form.
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Check It Out Example 2A Evaluate the expression
c for each value of c. Write each answer
in simplest form. c
c
Substitute for c.

Multiply.
The answer is in simplest form.
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Check It Out Example 2B c
c
Substitute for c.

1
Use the GCF to simplify.

2
Multiply.
The answer is in simplest form.
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Check It Out Example 2C c
c
Substitute for c.

Multiply.
The GCF of 4 and 28 is 4.
The answer is in simplest form.
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Lesson Quiz
Multiply. Write each answer in simplest form. 1.
2. Evaluate the expression x for each
value of x. Write the answer in simplest form.
3. x 4. x 5. At a particular college
of the students take a math class. Of these
students, take basic algebra. What fraction
of all students take basic algebra?