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 %

 

Original Script, LeMieux, 2001
Enhanced, 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

Return to ...
C.a.R. Main Page