PSAT Math Multiple-Choice Question 492: Answer and Explanation

Question: 492

Based on the data John collected, over which of the following intervals is there a positive relationship between his caffeine intake, in milligrams per hour, and his reading speed, in pages per hour?

• A. 40–60 and 60–75
• B. 40–60 and 80–100
• C. 25–40 and 40–60
• D. 25–40, 60–80, and 100–120

Correct Answer: B

Explanation:

B

The question asks about which intervals on the graph demonstrate a positive relationship. A positive relationship is one in which both variables increase together, resulting in a positive slope. From the graph, the only intervals that demonstrate a positive relationship between caffeine intake and reading speed are between 40–60 mg/hour and 80–100 mg/hour. The correct answer will contain only these intervals. Eliminate (A), (C), and (D). The correct answer is (B).