PSAT Math Multiple-Choice Question 69: Answer and Explanation

Question: 69

A group of students decided to have a car wash to raise funds for the school. The students charged the same rate to wash each car, and they paid for cleaning supplies out of the proceeds. If the net amount, N(c), in dollars, raised from washing c cars is given by the function N(c) = 8c - 0.40c, which of the following can be deduced from the function?

• A. The students paid a total of $8 for cleaning supplies.
• B. The students paid a total of $40 for cleaning supplies.
• C. The students paid $0.40 per car for cleaning supplies.
• D. The students paid $8 per car for cleaning supplies.

Correct Answer: C

Explanation:

C

The question asks what can be deduced from the given function. Label the parts of the equation to determine what they represent. In this question, N(c) is the net amount the students raised, and c is the number of cars washed. The question also says that the students paid for cleaning supplies. The number 0.40 is multiplied by the number of cars and subtracted, so it must have something to do with the cost of the cleaning supplies. Next, use Process of Elimination to get rid of answer choices that are not consistent with the labels. Choices (A) and (D) associate the number 8 with the cleaning supplies, so eliminate (A) and (D). Choice (B) says that the students paid a total of $40 for the cleaning supplies, but the number in the equation is 0.40, not 40, and it is multiplied by the number of cars, so it is not a total. Eliminate (B). Choice (C) matches the given function. The correct answer is (C).