To determine the numeric value of a percentage of a whole number, convert the percentage into a decimal by moving the decimal point two places to the left, and multiply that by the whole number. For example, to find 50 percent of 20, multiply .50 by 20 to get 10.
"Percent" means "out of 100," and percentages are simply a quick way of writing fractions with a denominator of 100. For example, 72 percent is 72/100. To figure out what percentage one number (number A) is of another number (number B), divide number A by number B and multiply the answer by 100. For example, to determine what percentage 6 is of 24, first divide 6 by 24 to get .25. Multiply that value by 100 to get your answer: 25 percent.
Understanding how to use percentages is useful for calculating discounts. When stores have sales offering a certain percentage off, figure out the final price in one of two ways. If an item is 40 percent off, for example, you can calculate 40 percent and then subtract that value from the original price. However, since 40 percent off is the same as 60 percent of the original price, you can save yourself a step by simply multiplying the original price by .60.