8.4 Percent of Increase and Decrease

1
8.4 Percent of Increase and Decrease
2
Percent change is the ratio of the amount of
change to the original amount.
Percent increase describes how much the original
amount increases.
Percent decrease describes how much the original
amount decreases.
3
Find the percent increase or decrease from 16 to
12.
Is this percent an increase or decrease?
16 12 4 First find the amount of change.
Think What percent is 4 of 16?
Set up the ratio.
4
Continued
Reduce the fraction or find the decimal form.

25 Write as a percent.
From 16 to 12 is a 25 decrease.
5
Try This
Find the percent of increase or decrease from 15
to 20.
Is this percent an increase or decrease?
20 15 5 First find the amount of change.
Think What percent is 5 of 15?
Set up the ratio.
6
Continued
Reduce the fraction if possible.
0.33 Find the decimal form.
33 1 Write as a percent.
3
1
From 15 to 20 is a 33 increase.
3
7
Percent Decrease
Sarah bought a DVD player originally priced at
450 that was on sale for 20 off. What was the
sale price?
450 ? 20 First find 20 of 450.
450 ? 0.20 90 20 0.20
The amount of decrease is 90.
Think The reduced price is 90 less than 450.
450 90 360 Subtract the amount of
decrease.
The sale price of the DVD player was 360.
8
Percent Increase
Mr. Olsen has a computer business in which he
sells everything at 40 above the wholesale
price. If he purchased a printer for 85
wholesale, what will be the retail price?
85 ? 40 First find 40 of 85.
85 ? 0.40 34 40 0.40
The amount of increase is 34.
Think The retail price is 34 more than 85.
85 34 119 Add the amount of increase.
The retail price of this printer will be 119.