PSAT Math Grid-Ins Question 105: Answer and Explanation

Question: 105

Charlie uses apple juice and cherry juice to make a punch for his birthday party. The expression 1.9a + 2.2c = 13.9 models the recipe Charlie uses to make the punch, where a and c are the volumes, in liters, of apple juice and cherry juice, respectively. How many liters of cherry juice does Charlie need for the recipe if he uses 5 liters of apple juice?

Correct Answer: 2

Explanation:

2

The question asks for the value of a variable in an equation. Since the amount of apple juice is given as 5 liters, plug 5 in for a. The new equation becomes 1.9(5) + 2.2c = 13.9, or 9.5 + 2.2c = 13.9. Subtract 9.5 from both sides of the equation to get 2.2c = 4.4, then divide both sides by 2.2 to get c = 2. The correct answer is 2.