Basic Math and Pre-Algebra: 1,001 Practice Problems For Dummies (+ Free Online Practice)
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Percents are commonly used in business to represent partial amounts of money. They're also used in statistics to indicate a portion of a data set. As you practice basic math problems, you'll discover that percents are closely related to decimals, which means that they're easier to work with than fractions.

  • To change a percent to a decimal, move the decimal point two places to the left and drop the percent sign.

  • To change a decimal to a percent, move the decimal point two places to the right and attach a percent sign.

  • To change a percent to a fraction, drop the percent sign and put the number of the percent in the numerator of a fraction with a denominator of 100. If necessary, reduce the fraction.

  • To change a fraction to a percent, first change the fraction to a decimal by dividing. Then change the decimal to a percent by moving the decimal point two places to the right and attaching a percent sign.

  • Calculate simple percents by dividing. For example, to find 50% of a number, divide by 2; to find 25%, divide by 4; to find 20%, divide by 5; and so forth.

  • You can calculate some percents by reversing the numbers. For example 14% of 50 is the same as 50% of 14, which equals 7.

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Mark Zegarelli is a math and test prep tutor and instructor in San Francisco and New Jersey. He is the author of Basic Math & Pre-Algebra For Dummies, SAT Math For Dummies, ACT Math For Dummies, Logic For Dummies, and Calculus II For Dummies.

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