Title: Lesson Presentation
1Warm Up
Problem of the Day
Lesson Presentation
2Warm Up Multiply. Write each answer in simplest
form. 1. 2 2 2. 1 3 3. 3
3 4. 2 1
5
or 5
10
or 2
3Problem of the Day Rachel is building a
doghouse. She needs to cut a 12-foot-long board
into lengths of 65 in. How many lengths can she
cut, and will there be any wood left? If so, how
much?
2 cuts yes, 14 in.
4Learn to divide fractions and mixed numbers.
5Vocabulary
reciprocal
6Reciprocals can help you divide by fractions. Two
numbers are reciprocals if their product is 1.
7Additional Example 1A Finding Reciprocals Find
the reciprocal.
of is 1.
The reciprocal of is 9.
8Additional Example 1B Finding Reciprocals Find
the reciprocal.
Think of what number is 1?
of is 1.
1
The reciprocal of is .
9Additional Example 1C Finding Reciprocals Find
the reciprocal.
Write 3 as .
1
of is 1.
1
The reciprocal of is .
10Check It Out Example 1A Find the reciprocal.
of is 1.
The reciprocal of is 4.
11Check It Out Example 1B Find the reciprocal.
Think of what number is 1?
of is 1.
1
The reciprocal of is .
12Check It Out Example 1C Find the reciprocal.
Write 4 as .
1
of is 1.
1
The reciprocal of is .
13Look at the relationship between the fractions
and . If you switch the numerator and
denominator of a fraction, you will find its
reciprocal. Dividing by a number is the same as
multiplying by its reciprocal.
24 4 6
24 6
14Additional Example 2A Using Reciprocals to
Divide Fractions and Mixed Numbers Divide. Write
each answer in simplest form.
7
7
Multiply by the reciprocal.
The answer is in simplest form.
15Additional Example 2B Using Reciprocals to
Divide Fractions and Mixed Numbers
Rewrite as multiplication using the reciprocal of
, .
1
Simplify before multiplying.
2
Multiply.
You can write the answer as a mixed number.
1
16Additional Example 2C Using Reciprocals to
Divide Fractions and Mixed Numbers
2 1
Write the mixed numbers as improper fractions. 2
and 1
2 1
Rewrite as multiplication.
3
Simplify before multiplying.
1
Multiply.
You can write the answer as a mixed number.
2
17Check It Out Example 2A Divide. Write each
answer in simplest form.
3
3
Multiply by the reciprocal.
The answer is in simplest form.
18Check It Out Example 2B
Rewrite as multiplication using the reciprocal of
, .
1
Simplify before multiplying.
2
Multiply.
You can write the answer as a mixed number.
3
19Check It Out Example 2C
3 1
Write the mixed numbers as improper fractions. 3
and 1 .
3 1
Rewrite as multiplication.
3
Simplify before multiplying.
1
Multiply.
You can write the answer as a mixed number.
3
20Lesson Quiz
Find the reciprocal. 1. 2. Divide. Write
each answer in simplest form. 3. 20 4. 3
2 5. Rhonda put 2 pounds of pecans into
a -pound bag. How many bags did Rhonda
fill?
, or 1
11 bags