PSAT Math Multiple-Choice Question 531: Answer and Explanation

Question: 531

A teacher uses 2 dry erase markers for every student in his class each year. He also needs 1 red pen for every 5 students. If he determines that he will need 7 red pens for the upcoming school year, which of the following could be the number of dry erase markers that he expects to use?

• A. 50
• B. 60
• C. 70
• D. 80

Correct Answer: C

Explanation:

C

The question asks for the number of dry erase markers the teacher expects to use for a certain number of students. Begin by reading the question to find information about the number of red pens. The question states that the teacher uses 1 red pen for every 5 students. Set up a proportion to determine how many students the teacher has if he needs 7 red pens, being sure to match up units: . Cross-multiply to get x = 35 students. If the teacher uses 2 dry erase markers for each of the 35 students, he will use 2(35) = 70 dry erase markers. The correct answer is (C).