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Percentage calculations come into play in many real-world situations, such as determining how much to tip in a restaurant and figuring out the discounted prices of clothing. Here's how to do these calculations.

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An individual calculates year-over-year percentage change, or YOY change, by evaluating two or more measurements and comparing them to the same period of time in a previous year.

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The easiest way to calculate a percentage is taking 10 percent of any number and multiplying it to find the percentage desired. To calculate 10 percent of a number, simply move the decimal point one place to the left.

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To calculate a weighted percentage, first multiply each item by the percentage it has been allotted, and then add those values together. Weighted percentages help in situations where certain factors are more important than others.

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Percent simply means "per 100," so any percentage number can be expressed as number/100. For example, 75 percent can be expressed as the fraction 75/100 or as the decimal fraction 0.75.

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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.

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An element's radioactive decay can be determined through a single equation which requires imputing the isotope's half life, its rate of decay and the decay time since the rate of decay is measured.

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With a regular calculator using basic math functions, it is possible to calculate percentages. To calculate percentages on a regular calculator, find the difference between the two numbers be compared, then divide that number by the original number and multiply by 100. The result is a percent increa

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Subtracting a past population value from the present population value, and dividing this result by the past population value, yields the population-growth rate. Multiplying the population-growth rate by 100 yields the growth percentage.

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To calculate a percentage of $1.00, treat it as 100 pennies. The percentage sought is equal to the same number in cents. According to Math Is Fun, "percent" is a number per 100, so treating $1.00 as a 100 pennies makes the math simple.