2. Main Idea and New Vocabulary Key Concept: Percent of Change
Example 1: Find Percent of Increase
Example 2: Find Percent of Decrease
Lesson Menu

3. Find the percent of increase or decrease.
percent of change
percent of increase
percent of decrease
Main Idea/Vocabulary

4. Key Concept

5. Find Percent of Increase
SHOPPING Jonas has been saving for a video game. Last year it cost $28. This year it costs $36. Find the percent of change in the cost. Round to the nearest whole percent if necessary. Then state whether the percent of change is an increase or decrease.
Step 1 Find the amount of change.
$36.00 – $28.00 = $8.00
Step 2 Find the percent of change.
percent of change =
Example 1

6. Find Percent of Increase
= Substitution
≈ 0.29 Simplify.
≈ 29% Write 0.29 as a percent.
Answer: The percent of change is 29%. Since the percent of change is positive, this is a percent of increase.
Example 1

7. SOCCER The fee to join a soccer club is $30
SOCCER The fee to join a soccer club is $30. Next month the fee will go up to $36. Find the percent of change in the cost. Round to the nearest whole percent if necessary. Then state whether the percent of change is an increase or decrease.
A. –20%; decrease
B. 20%; increase
C. –83%; decrease
D. 83%; increase
Example 1 CYP

8. Find Percent of Decrease
LIBRARY Last month 349 books were checked out from the school library. This month, 273 books were checked out. Find the percent of change in the number checked out. Round to the nearest whole percent if necessary. Then state whether the percent of change is an increase or decrease.
Step 1 Find the amount of change.
270 – 349 = –79
Example 2

9. Find Percent of Decrease
Step 2 Find the percent of change.
percent of change =
= Substitution
≈ –0.22 Simplify.
≈ –22% Write –0.22 as a percent.
Example 2

10. Find Percent of Decrease
Answer: The percent of change is –22%. Since the percent of change is negative this is a percent of decrease.
Example 2

11. RUNNING Last year 122 people ran in a 5K race
RUNNING Last year 122 people ran in a 5K race. This year 110 people ran in the race. Find the percent of change in the number of people who ran the race. Round to the nearest whole percent if necessary. Then state whether the percent of change is an increase or decrease.
A. –10%; decrease
B. 10%; increase
C. –12%; decrease
D. 12%; increase
Example 2 CYP