Henrico County Public Schools

# Solving Percent Increase/Decrease Problems

There is one method you can use to solve both percent increase and percent decrease problems. Here you will learn more about the POWER of proportions.

#### Example 1:

The number of students enrolled at the J. R. Smith School has decreased from 800 students to 700 students. What is the percent decrease?
Arrange the original value and 100% on the bottom and the change and x% on the top. Write the proportion and follow the steps on the right.
Example 1:

#### Example 2:

Last year the price of a Wonderful Whopper was \$2.40. This year the price increased to \$2.70. By what percent did the price increase?

Arrange the original value and 100% on the bottom and the change and x% on the top. Write the proportion and follow the steps on the far right.
Example 2:

### Proportional Percent Increase/Decrease Calculator

 Enter the values from your proportion. Place an x for the unknown in the appropriate box, then click on Calculate. Change Original = % 100 % Check your set-up! Original Script, LeMieux, 2001Enhanced, Lapinski, 2003

### Percent Increase or Decrease Problems

To find the percent of increase or decrease remember that the proportion is always the following:

The correct answers are provided so you can determine if you placed the numbers appropriately.

Increase Example: A company’s stock rose from \$12 per share to \$21 per share. Find the percent of the increase.

Amount of the increase is \$21 - \$12 = \$9
Original value = \$12. (Answer 75%)

Decrease Example: The temperature at noon was 96° and at midnight was 72°. Find the percent of the decrease.

Amount of decrease is 96 - 72 = 24
Original value = 96. (Answer 25%)

LESSONS

Find Percent

Find the Whole

Find the Part

Increase/Decrease