Math Percentage Problems and Practice Drills

How Do I Solve Simple Math Percentage Problems?

One way to solve many simple percentage problems is to use multiplication. Remember to point out to your child that the word 'of' used in a problem often indicates that you use multiplication to solve it. Consider the following problem: find 10% of 100. Begin by changing the percentage to a decimal so that 10% is rewritten as 0.10. Then, as indicated by the word 'of', multiply 0.10 by 100, which equals 10.

An alternative way to solve simple math percentage problems is to set up a proportion. On the percent side of the proportion, you should write a fraction with the percent on top and 100 in the denominator. On the other side of the proportion, write the large number (the whole) on the bottom and the smaller number (the part) on top. For example, if you want to set up a proportion showing that 10 is 50% of 20, you should write 10/20 = 50/100.

Sample Percentage Problems

Drills

1. What is 12% of 500?

Begin by changing 12% to a decimal (0.12). Then, multiply. The equation should look like this: 0.12 x 500 = 60.

2. What is 60% of 4,800?

The answer is 2,880.

3. What is 45% of 1,000?

The answer is 450.

4. Find 4% of 320.

For this problem, you would use the equation .04 x 320 to get an answer of 12.8.

5. What percent of 50 is 25?

For a challenge, try rephrasing the problem. Rewrite the above problem like this: 25 = x (50). Then, solve for x by dividing both sides by 50. As a result, 25 is 50% of 50. This can prepare your child for using a variable in an equation.

6. What percent of 60 is 20?

To solve, set up the following proportion: 20/60 = x/100. Then solve for x by multiplying 100 by 20 and then dividing the sum by 60. After solving, the proportion should look like this: 20/60 = 33/100. As a result, 20 is 33% of 60.

Word Problems

1. Maddy went to the store and picked out $28.50 in clothing. The sales tax is 9.5%. How much will Maddy spend in all?

Begin by multiplying 28.5 by 0.095, which equals 2.7. Then, add 2.7 to 28.5. As a result, Maddy will spend $31.20.

2. Tim bought shoes that were $52.10 before tax. The total cost was $54.95. What percent was the sales tax?

Begin by subtracting: 54.95 - 52.10 = 2.85. Then, calculate what percent 2.85 is of 54.95 by solving the following equation: 2.85 = (x)(54.95). For this equation, x is about 0.052. As a result, the sales tax is 5.2%.