# ACT Practice Math Questions: Percentages

If you want a high percentage score on the ACT Math exam, then you should know how to solve percentage problems. As you’ll see in the following practice questions, percentages appear in a wide range of problems, from business math to algebra.

## Practice questions

- Given that 6 percent of (
*a*+*b*) = 12 percent of*b,*which of the following must be true?**A.***a*<*b*

**B.***a*>*b*

**C.***a*=*b*

**D.***a*+*b*= 0

**E.***a*< 0 and*b*< 0 - The cost of a tablet increased 25 percent from 2014 to 2015. In 2016, the cost of the tablet was 1/4 less than its 2014 cost. By what percentage did the cost of the tablet decrease from 2015 to 2016?
**A.**5%

**B.**25%

**C.**40%

**D.**50%

**E.**75%

## Answers and explanations

- The correct answer is Choice
**(C).**An easy way to deal with percentages is to use the number 100. In this case, say that (

*a*+*b*) = 100. Then 6 percent of 100 = 6. That means that 12 percent of*b*is 6. Solve for*b*:

If*a*+*b*= 100, then*a*= 50 and*a*=*b*. - The correct answer is Choice
**(C).**Give this problem a real value to work with. Say the 2014 price of the tablet is $100. If the price increased 25 percent between 2014 and 2015, its 2015 price is $125. The next year the price was 1/4 less its 2014 price of $100, which means it cost $75 in 2016. To find the percent decrease between 2015 and 2016, subtract the two prices and divide the difference by the 2015 price:

The percent decrease from 2015 to 2016 is 40 percent.