8.4 Percent of Change

Percent of Change

Definitions

• Percent of Change - the percent by which a number increases or decreases.

• Percent Decrease - a percent change describing a decrease in a quantity.

• Percent Increase- The percent change describing an increase in a quantity.

What kind of Percent of Change

Percent Change

describes how much a quantity decreases or increases in relation to the original amount

for example: the percent off in this sale is the percent change

Calculating Percent Change

Example 1

The enrollment at a middle school increased from 650 students to 780 students in 5 years. What is the percent increase in the number of students enrolled at the school?

Example 1

Multiple Choice

Before you can find the percent of increase, what value do you need to calculate?

• change in prices

• sum of prices

• quotient of prices

• product of prices

Example 2

Multiple Choice

How do we write the second ratio for this proportion?

$$\frac{x}{100}=$$  

• $$\frac{1.80}{1.50}$$  

• $$\frac{1.80}{3.30}$$  

• $$\frac{1.50}{1.80}$$   

• $$\frac{1.50}{3.30}$$  

Example 2

Multiple Choice

Which proportion could you use to find the percent of decrease?

• $$\frac{x}{100}=\frac{6.3}{25.2}$$

• $$\frac{x}{100}=\frac{6.3}{18.9}$$

• $$\frac{x}{100}=\frac{25.2}{18.9}$$

• $$\frac{25.2}{100}=\frac{x}{18.9}$$

Example 3

Multiple Choice

If you have a percent increase problem, your original amount gets...

• bigger

• smaller

Multiple Choice

If you have a percent decrease problem, your original amount gets...

• bigger

• smaller

Multiple Choice

1. Find the PERCENT of change.

20 dogs to 5 dogs

• Decrease 15%

• Increase 15%

• Increase 75%

• Decrease 75%

Multiple Choice

2. Find the PERCENT of Change.

The original cost was $50 and the new cost is $60.

• Increase 20%

• Increase 16.67%

• Increase $10

• Decrease $10

Multiple Choice

3. Find the percent of change if Eddie started with 20 tickets and ended with 30 tickets.

• Increase 10 tickets

• Increase 50%

• Increase 33%

• Decrease 50%

Multiple Choice

4. Last week, you finished level 2 of a video game in 32 minutes. Today, you finished level 2 in 28 minutes. What is your percent of change?

• Increase 12.5%

• Decrease 12.5%

• Increase 4%

• Decrease 4%

Multiple Choice

5. Ann works in a supermarket for $10.00 per hour. She received a raise to $12.00. What is the percent of change in her hourly wage?

• Increase 16.67%

• Decrease 16.67%

• Increase 20%

• Decrease 20%

Multiple Choice

6. One week, 72 people got a speeding ticket. The next week, only 36 people got a speeding ticket. What is the percent of change in the speeding tickets?

• Increase 50%

• Decrease 50%

• Increase 1%

• Decrease 1%

Multiple Choice

7. Mary lost 30 pounds. Before her diet she weighed 180 pounds. What is the percent of change?

• 17% Decrease

• 19% Decrease

• 25% Decrease

• 20% Decrease

Multiple Choice

8. Mrs. Boyd has 35 students in her science class.If her class increases to 42 students next year, what will be the percent of change?

• 20% decrease

• 75% increase

• 93% increase

• 33% decrease

Multiple Choice

9. Last year, 2,376 people attended a summer music festival. This year, attendance was 2,950. What was the percent of change in attendance to the nearest whole percent?

• Increase 24%

• Increase 19%

• Decrease 24%

• Decrease 19%

Multiple Choice

What is the percent of change? 55 mph to 70 mph

• 27% increase

• 27% decrease

• 21% increase

• 21% decrease

Multiple Choice

If a school of 900 students got 50 more students, will the change be an increase or decrease?

• Increase

• Decrease

Multiple Choice

The average number of shirts sold in the beach shop was 285 on Saturday in the summer. As the temperature went lower, the average number of shirts decreased to 114 every Saturday. What was the percentage decrease of in the average number of shirts sold in the shop?

• 60%

• 40%

• 150%

• 171%

Multiple Choice

And one final one before you try some on your own:

In the Winter, Luna picked 125 apples from her apple tree, but in the Summer, she picked 175. By what percent did the amount of apples she picked increase?

• 71%

• 4%

• 29%

• 40%

Now...

Finish your notes from yesterday.