##### ACT
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

1. 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

2. 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%

1. 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.

2. 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.

Lisa Zimmer Hatch, MA, and Scott A. Hatch, JD, have been helping students excel on standardized tests and navigate the college admissions process since 1987. They have written curricula and taught students internationally through live lectures, online forums, DVDs, and independent study.