PSAT Math Multiple-Choice Question 493: Answer and Explanation

Question: 493

John wants to estimate what his reading speed would be, in pages per hour, if he were to consume 45 mg of caffeine in an hour. Using the trend that he observed between 40 and 60 milligrams per hour, which of the following is closest to the reading speed, in pages per hour, that John can expect?

• A. 13
• B. 15
• C. 17
• D. 20

Correct Answer: C

Explanation:

C

The question asks for a certain value on a graph given an observed trend. There is no line of best fit for the interval between 40 and 60 mg/hour, so draw one in using the answer sheet as a straight edge if necessary. The variable mg/hour is listed along the horizontal axis, so find 45 on that axis. From this point, trace up to find the intersection with the line of best fit, again using the answer sheet as a straight edge. Now trace over to the vertical axis to find the corresponding value on the Reading Speed axis. The intersection will be somewhere between 15 and 20 pages/hour. Only the value in (C) falls between 15 and 20 pages/hour. The correct answer is (C).