Henrico County Public Schools

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?

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 |
## Percent ProblemsThe correct answer is provided to determine if you placed the numbers appropriately. 18 is 60% of what number?Example 1: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? |