How to Figure Percentages of a Whole Number
In everyday life, it is common place to deal with percentages of whole numbers. As is often the case when you go to a store, and see a sign that say, "20 percent off." The item you want to purchase is $15, which is a whole number, and you need to figure out what 20 percent of 15 equals. .
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Instructions
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1
Change the percent to a decimal. If the problem you are trying to figure out is 30 percent of 60, then you have to change 30 percent to 0.30. Remember, 30 percent is the same as 3 tenths or 30 hundredths, which is 0.3 or 0.30. It doesn't matter which way you write it, both numerals represent the same amount.
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2
Use a calculator or paper and pencil to figure a percentage of a whole number. If you are trying to figure 30 percent of 60 as in Step 1, then you would punch into your calculator, or write on your piece of paper, "0.30 x 60 =" You will get an answer of 18 if you punch in the correct numbers or multiply correctly on your paper.
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3
Change the percent into a fraction, especially if it is a common and easy fraction. Remember, percents are always out of 100. So, if you have a percent such as 20 percent, then with the fraction, 20 becomes the numerator, and 100 becomes the denominator. The fraction for 20 percent would be 20/100. The fraction for 60 percent would be 60/100. You will always want to simplify the fractions to their lowest form before you figure the percentage of a whole number.
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4
Reduce the fractions to simplest form. For example, if you are trying to figure 25 percent of 40, you can change 25 percent to the fraction 1/4. Here's how: 25 percent is the same as 25/100 as you learned in Step 3. When you reduce 25/100 by dividing both the numerator and denominator by 25, you get the fraction 1/4. Can you figure 1/4 of 40? That is the same as taking 40 and dividing it into 4 equal parts. The answer is 10. It is much easier to figure 25 percent of 40 when you have simplified the fraction to 1/4.
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5
Decide if you want to use decimals or fractions to figure out the answer by looking at the percent. If the percent is divisible by 5 such as 20 or 30, you will probably want to use fractions--especially if it is a percentage below 50%. If it is an odd number such as 67 percent or 92 percent, it is probably easier to change the percents into a decimal and then multiply the decimal and the whole number.
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Tips & Warnings
When you multiply decimals without a calculator on paper, remember that when you get your answer you have to count how many decimal places are in your problem, and make sure you put that amount of places after the decimal point in your answer.
Don't rely too much on a calculator. Many percentages of whole numbers can be figured in your head easily, especially when you have practiced a lot. It may take longer to punch in the numbers on a calculator, than it does to figure the problem out in your head.
Resources
- Photo Credit percent icon image by Dmitri MIkitenko from Fotolia.com
