CHAPTER 7
Percents
7-1. Percent of Change
The word percent means hundredth or out of every hundred.
To write a decimal or a fraction as a percent, multiply the decimal or the fraction by 100 and add the % sign.
Convert the fraction to decimal.
1
To write a percent as a decimal or a fraction, multiply the percent by , and drop the % sign.
100
Simplify the fraction.
Example 1 Write each decimal or fraction as a percent.
3
a. 0.65 b.
16
Solution a. 0.65 0.65 100% 65% Multiply the decimal by 100 and add the
% sign.
3 3 300
c. 100% % 18.75% Multiply the fraction by 100 and add the
16 16 16 % sign. Convert the fraction to decimal.
Example 2 Write 175% as a decimal and a fraction.
1 175 1
Solution 175% 175 1.75 Multiply the amount of percent by ,
100 100 100
and drop the % sign. Simplify the fraction.
1 175 7
175% 175
100 100 4
The percent a quantity increases or decreases from its original amount is the percent of change.
amount of increase amount of decrease
percent increase percent decrease
original amount original amount
Example 3 a. A $300 tablet is on sale for $234. What is the percent of discount?
b. The population of Sunny Hills increased from 12,000 to 15,840 in ten years.
What is the percent increase of the population?
amount of discount
Solution a. percent discount
original amount
300 234 66
0.22
300 300
There was a 22% discount.
number of increase
b. percent increase
original number
15,840 12, 000 3,840
0.32
12, 000 12, 000
There was a 32% increase in population.
110 Chapter 7
Exercises - Percent of Change
1 5
Which of the following is equivalent to 0.03 % The temperature increased from 60 F to 72 F .
of 4? What is the percent increase in temperature?
A) 0.12 A) 15%
B) 0.012 50
B) %
C) 0.0012 3
D) 0.00012 C) 20%
70
D) %
3
2
1
400
6
A) 0.25% This year’s enrollment in Mesa School District
B) 0.025% is 6,000, which is 20 percent higher than last
year’s. What was last year’s enrollment in Mesa
C) 0.0025% School District?
D) 0.00025%
3
The quantities x and y are positive. If x is
decreased by 20 percent and y is increased by
20 percent, then the product of x and y is
A) unchanged
B) decreased by 4% 7
C) increased by 5% If 125% of x is 80 and x is n % of 400, what is
the value of n ?
D) decreased by 6%
By what percent is 4.5 105 greater than 9 104 ?
A) 200%
B) 400%
C) 500%
D) 600%
