How to Solve Percentage Problems

Help students conquer percent problems.
••• Hemera Technologies/AbleStock.com/Getty Images

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.

    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

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

Related Articles

How to Find the Answer to 20% of What Number Is 8?
How to Find Out How Much 6% Is of a Number
How to Use the Percentage Key on a Calculator
How to Teach Math Percentages to 6th Grade
How to Calculate Percent Decline
How to Calculate the Percent of One Hour
How to Calculate Order of Magnitude
How to Figure a Percentage of a Whole Number
How to Divide a Percent Using a Calculator
How to Calculate Percent Slope
How to Increase a Number by a Percentage
How to Calculate the Percent Weight Per Volume
How to Find Y Value for the Slope of a Line
How to Calculate the Percentage of Another Number
Impress Your Date on Valentine's by Calculating the...
How to Find the Fractional Part of a Number
Tricks to Solving Percentage Word Problems
How to Calculate Percent of Return
SAT Math Prep II: Exponents, Ratios and Percentages