Percentage problems such as "50 is 20 percent of what number?" and "What percent of 125 is 75?" are often difficult for students. Teaching students an easy method of substitution will have them conquering percentage problems in no time.

Be sure you put the numbers in the right spots in the equation, or else your answer will be incorrect.

Write the proportion x/100 = is/of. x is the percentage (over 100 of course), "is" refers to the part, and "of" refers to the whole.

Fill in what you know. In the question "50 is 20 percent of what number?", x=20, is=20 ("50 is"), and of=the unknown ("of what number"). Therefore, write 20/100=50/x.

Cross multiply. You'll have a constant on one side and a number times a variable on the other side. Here, it is 20x=5,000.

Solve for x. Here, x=5,000/20=250, which is the answer.

Practice by solving the other problem, "What percent of 125 is 75?" First, write, x/100=is/of. In this example, x is the unknown, is=75 ("is 75"), and "of"=125 ("of 125"). Fill in what you know to get x/100=75/125. Cross multiply to get 125x=7,500. x=60, which is the percent.

#### Warnings

About the Author

This article was written by the CareerTrend team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about CareerTrend, contact us [here](http://careertrend.com/about-us).

Photo Credits

Hemera Technologies/AbleStock.com/Getty Images