# ASVAB Mathematics Knowledge Practice: Percentages

The Mathematics Knowledge subtest on the ASVAB contains many problems that involve working with percentages. Although calculating percentages is pretty straightforward, you will definitely find a scratch paper and pencil useful, as you’ll see in the following practice questions.

## Practice questions

- 250 is 40 percent of what number?
**A.**650

**B.**625

**C.**6,250

**D.**6,500 - What is 55 percent of 150?
**A.**75

**B.**83.5

**C.**80

**D.**82.5

## Answers and explanations

- The correct answer is
**Choice (B).**To determine a whole number when you know a part and a percent, you can use a proportion; let

*x*equal the whole. The proportion looks like this:Plug in the numbers you know:

Cancel out the zeros in the fraction to make the problem a bit easier:

(Remember, though, you can’t cancel out zeros on the other side of the equals sign.)

Divide both sides by 4 to isolate*x*:You can check your work by putting the variable in the original equation and making sure the fractions are equal:

- The correct answer is
**Choice (D).**You can convert 55 percent into a decimal (0.55) and multiply it by 150 to arrive at the answer, which is 82.5, or you can use a proportion where

*x*equals the number you need to find:Cross-multiply:

Divide each side by 100 to isolate

*x*:

You can’t use a calculator on the ASVAB, so figure out which method of finding percentages is easiest for you before you take the test.