Using Equations to Solve Percent Problems

Objective: Learn to use equations to solve problems involving percents.

One way to solve percent problems is by writing an equation. When writing an equation you must remember the following:

The word of means multiply ( × )

The word is means equals ( = )

Rewrite percents as decimals.

what number stands for the variable N

What percent stands for the variable P

Example 1:

What percent of 48 is 15 ? Steps: P × 48 = 15 1. Write the equation. 48 48 2. Use inverse operations. 3. Divide P = 0.3125 4. Write the decimal as a

P = 31. 25% percent.

Example 2:

12 % of what number is 9?

0.12 × N = 9 0.12 0.12

N = 75

Steps:1. Write the equation.2. Convert the percent to a decimal. 3. Use the inverse operation. 4. Cancel5. Divide6. Write answer

Example 3:

What number is 25% of 200?N = 25% × 200N = 0.25 × 200N = 50

Steps:1. Write the equation.2. Change the percent

to a decimal. 3. Multiply

Your Example:

What percent of 78 is 39?

55% of 985 is what number?

30% of what number is 45?

Homework: Solve each problem.

1. What percent of 70 is 22?

2. 9% of 600 is what number?

3. 11% of what number is 36?

4. 95% of 40 is what number?

5. 89% of what number is 178?

6. What percent of 72 is 67?

7. 240% of 58 is what number?

8. What percent of 65 is 30?

9. 18% of what number is 12?

10. 40% of 50 is what number?