How to Work Out Math Percentages

It's easier to think of a percentage as a portion of 100.

Working out math percentages is simple if you understand the basic concept behind a percentage. Mathematically, a percentage (symbolized by "%") is a portion of one, but it is much easier to think of it as a portion of 100. For example, if 50 percent of a school's students are girls, for every 100 students, 50 of them are female. Annual percentage rate, or APR, is a good example of every day use of percentage.

Things You'll Need

• Calculator

Instructions

1. To begin working out a percentage, determine the percentage you need. For example, you have 10 red apples and 90 green apples, and you want to know how to work out what percentage of apples are red.

2. Determine how many items you have in all. In this example, there are 100 apples.

3. Divide the number you need the percentage for by the other number. In the example, divide 10 by 100 to get 0.10.

4. To work out the percentage, multiply your answer by 100. In the example, you get 10, which means 10 percent of the total number of apples were red. If you solve for the percentage of green apples, the answer would be 90 percent.

5. Think about your answer and make sure it makes sense. If you made the common mistake of dividing the numbers backward, you would have ended up with 1,000 percent, which doesn't make sense in the context of the problem.

Tips & Warnings

• Practice percentages with whole numbers that are multiples of each other; they will multiply and divide easily.

• Don't forget to multiply by 100 or your percentage will be off by two units of 10.

References

• Helping With Math: Calculating Percentages