Henrico County Public Schools

Find the Whole

Created by Steven Lapinski using the Compass and Ruler (C.a.R.) program.


Try solving these problems using the Part and X% sliders.
1. 16 is 25% of what number?
2. 30% of what number is 15?
3. If 4 are late to class and this is 16.67% of the class, How many students are in the class?


Solving Percent Problems

To solve percent problems, one begins by using a number line to help write a proportion. The next step is solving the proportion for the missing term. Remember that a percent is always some part of 100. We can set up a proportion where each side is a ratio. The following examples demonstrate using a number line and proportion to solve percent problem.


Example 2: 42 is 40% of what number? This can be rephrased as “42 is ‘some part’ of what number?” Arrange the parts at one end of the number line and the wholes at the other (see the figure on the far right) and the whole above the 100%. Write the proportion and follow the steps on the right. Example 2:

Proportional Percent Calculator


Enter the values from your proportion. Place an x for the unknown in the appropriate box, then click on Calculate.
Part
Whole

=

%
100 %

 

Original Script, LeMieux, 2001
Enhanced, Lapinski, 2003

Percent Problems


The correct answer is provided to determine if you placed the numbers appropriately.
Example 1: 18 is 60% of what number?
The correct answer is provided to determine if you placed the numbers appropriately.
This can be rephrased as “18 is what part of the whole?” Write the proportion. (Answer: 30)
Problems:
40% of what percent is 15? (Answer: 37.5)
25% of a number is 75? (Answer: 300)
80 is 125% of what number?

LESSONS

Find Percent

Find the Whole

Find the Part

Increase/Decrease

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