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# How do you add percentages?

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To add a percentage to a given number involves multiplying the base number by a decimal that represents the percentage fraction. Adding two percentages together involves the opposite, or converting the percentages to fractions.

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To calculate the addition or subtraction of percentages, it is first necessary to understand the relationship between a percentage and its decimal representation.

To Add a Percentage to a Given Number

Multiply the base number by 1 plus the percentage as a decimal. For example, to add 25 percent to the number 4: 4 x (1 + 0.25) = 4 x 1.25 = 5.

Convert the percentages to fractions with a common denominator and perform the simple addition operation. Then the answer may be converted back to a percentage. For example, to add 20 percent to 30 percent: 20 / 100 + 30 / 100 = 50 / 100 or 50 percent.

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## Related Questions

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One method to manually convert a fraction to a decimal is to multiply the denominator, the bottom number, by a number that will make the denominator a factor of 10. Then multiply the numerator, the top number, by the same number used on the denominator. Rewrite the fraction as a decimal using place values.

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To convert a percentage to a ratio, write out the percentage number as a fraction, reduce the fraction to its simplest form and convert the new fraction to a ratio by replacing the slash mark with a colon. Converting a percentage to a ratio takes only a few minutes and requires paper and a pencil.

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To find the percentage of a number, multiply the number by the percentage fraction. A percentage is a proportion between two quantities expressed in hundredths.