Warm Up

1

Warm Up
Problem of the Day
Lesson Presentation
2
Warm Up Multiply.
5 6
1.
3
23
2.
10
15
3. 0.05(2.8)
0.14
4. 0.9(16.1)
14.49
3
Problem of the Day Katie made a bookshelf that
is 5 feet long. The first 6 books she put on it
took up 8 inches of shelf space. About how many
books should fit on the shelf?
45
4
Learn to divide fractions and decimals.
5
Vocabulary
reciprocal
6
A number and its reciprocal have a product of 1.
To find the reciprocal of a fraction, exchange
the numerator and the denominator. Remember that
an integer can be written as a fraction with a
denominator of 1.
7
Multiplication and division are inverse
operations. They undo each other.
Notice that multiplying by the reciprocal gives
the same result as dividing.


8
Additional Example 1A Dividing Fractions
Divide. Write the answer in simplest form.
1 2
5 11
A.

Multiply by the reciprocal.
No common factors.
Simplest form
9
Additional Example 1B Dividing Fractions
Divide. Write the answer in simplest form.
3 8
2
2
B.

Write as an improper fraction.
Multiply by the reciprocal.
No common factors
19 16 1 R 3
10
Check It Out Example1A
Divide. Write the answer in simplest form.
7 15
3 4
A.

Multiply by the reciprocal.
No common factors.
Simplest form
11
Check It Out Example1B
Divide. Write the answer in simplest form.
2 5
3
4
B.

Write as an improper fraction.
Multiply by the reciprocal.
No common factors.
22 15 1 R 7
12
When dividing a decimal by a decimal, multiply
both numbers by a power of 10 so you can divide
by a whole number. To decide which power of 10 to
multiply by, look at the denominator. The number
of decimal places is the number of zeros to write
after the 1.

1 decimal place
1 zero
13
Additional Example 2 Dividing Decimals
Find 0.384 0.24.
Divide.
14
Check It Out Example 2
Find 0.585 0.25.
Divide.
15
Additional Example 3A Evaluating Expressions
with Fractions and Decimals
Evaluate the expression for the given value of
the variable.
5.25
for n 0.15
n
Divide.
16
Additional Example 3B Evaluating Expressions
with Fractions and Decimals
Evaluate the expression for the given value of
the variable.
4 5
k for k 5
Multiply by the reciprocal.
5
Divide.
17
Check It Out Example 3A
Evaluate the expression for the given value of
the variable.
2.55
for b 0.75
b
Divide.
18
Check It Out Example 3B
Evaluate the expression for the given value of
the variable.
4 7
u , for u 9
Multiply by the reciprocal.
No common factors
19
Additional Example 4 Problem Solving Application
A cookie recipe calls for cup of oats. You
have cup of oats. How many batches of cookies
can you bake using all of the oats you have?
The number of batches of cookies you can bake is
the number of batches using the oats that you
have. List the important information
20
Additional Example 4 Continued
Set up an equation.
21
Additional Example 4 Continued
Let n number of batches.
22
Additional Example 4 Continued
23
Check It Out Example 4
A ship will use of its total fuel load for a
typical round trip. If there is of a total
fuel load on board now, how many complete trips
can be made?
24
Check It Out Example 4 Continued
The number of complete trips the ship can make is
the number of trips that the ship can make with
the fuel on board. List the important information
25
Check It Out Example 4 Continued
Set up an equation.
Amount of fuel on board
Amount of fuel for one trip
Number of trips

26
Check It Out Example 4 Continued
Let t number of trips.
27
Check It Out Example 4 Continued
28
Lesson Quiz
Divide.
5 6
1 2
1.

2
1
2. 14 1.25
11.2
3. 3.9 0.65
6
112 x
4. Evaluate for x 6.3.
A penny weighs 2.5 grams. How many pennies would
it take to equal one pound (453.6 grams)?
5.
about 181