Page 309 - Algebra 1

L E S S O N Solving Problems Involving the Percent
47
of Change
Warm Up
1. Vocabulary A number that is part of 100 is the of the
(SB 5)
number.
Solve.
2. 60 is what percent of 80?
(42)
3. 20% of 40 is what number? (42)
4. 7 is 5% of what number? (42)
5. 25 is what percent of 80? (42)
New Concepts The percent of change is the ratio of the amount of change in a quantity to the original amount, expressed as a percent. The percent of change can be a
percent of increase or percent of decrease.
Finding the Percent of Increase or Decrease
Find the percent of change.
a. number of United States airports in 1985: 15,161 number of United States airports in 2005: 19,854
Example
1
Hint
Always subtract the original number from the new number to determine if the amount of change is an increase or decrease.
SOLUTION
≈ 0.31, or 31% The percent of increase is 31%.
b. number of taxicabs in the United States in 2001: 31,800 number of taxicabs in the United States in 2002: 30,800
19,854 - 15,161 = 4693 amount of increase = 4693
The difference is positive, so the percent of change is a percent of increase.
___ original amount 15,161
SOLUTION
≈ -0.03, or -3% The percent of decrease is 3%.
30,800 - 31,800 = -1000 amount of decrease = -1000
The difference is negative, so the percent of change is a percent of decrease.
___ original amount 31,800
Online Connection www.SaxonMathResources.com
294 Saxon Algebra 1