Pre-Algebra Chapter 6 - Ramsey School District

Example 2
Find the Percent
28 is what percent of 70? Estimate: 2 8
70 2 5
75 or 1 3 , which is 331 3 %.
You know that the base is 70 and the part is 28.
Let n represent the percent.
28 n(70)
2 8
n Divide each side by 70.
70
0.4 n Simplify.
So, 28 is 40% of 70. The answer makes sense compared to the estimate.
Example 3
Find the Base
18 is 45% of what number? Estimate: 18 is 50% of 36.
You know that the part is 18 and the percent is 45.
Let n represent the base.
18 0.45n Write 45% as the decimal 0.45.
18
0 .45n
0 .45
0.45
Divide each side by 0.45.
40 n Simplify.
So, 18 is 45% of 40. The answer is reasonable since it is close to the estimate.
DISCOUNT AND INTEREST The percent equation can also be used to
solve problems involving discount and interest. Discount is the amount by
which the regular price of an item is reduced.
Example 4
Find Discount
SKATEBOARDS Mateo wants to buy a skateboard. The regular price of
the skateboard is $135. Suppose it is on sale at a 25% discount. Find the
sale price of the skateboard.
Skateboards
The popularity of the
sport of skateboarding is
increasing. An estimated
10,000,000 people
worldwide participate
in the sport.
Source: International Association
of Skateboard Companies
Method 1
First, use the percent equation to find 25% of 135. Estimate: 1 of 140 = 35
4
Let d represent the discount.
d 0.25(135) The base is 135 and the percent is 25%.
d 33.75
Simplify.
Then, find the sale price.
135 33.75 101.25 Subtract the discount from the original price.
Method 2
A discount of 25% means the item will cost 100% 25% or 75% of the
original price. Use the percent equation to find 75% of 135.
Let s represent the sale price.
s 0.75(135) The base is 135 and the percent is 75%.
s 101.25 Simplify.
The sale price of the skateboard will be $101.25.
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Lesson 6-7 Using Percent Equations 299