People deal with percents all the time in everyday life. When sales clerks compute sales tax, they compute "7% of your total purchase." Similarly, when diners are deciding what size tip to leave, they compute "15% of the cost of our food." How do they perform these calculations?

Just as with fractions, the word "of" in a percent problem indicates multiplication. The sales clerk multiplies 7% by the total purchase, and the diner multiplies 15% by the cost of her food.

To find a percent of a number, first change the percent into a decimal or a fraction. Next, multiply that decimal or fraction by the number.

Example 1: What is 15% of 220?


I. Using decimals.

II. Using fractions.

Example 2: What is 12.5% of 52?


I. Using decimals.

II. Using fractions.