PSAT Math Multiple-Choice Question 141: Answer and Explanation

Question: 141

A pediatrician's office collects data on the heights of all its patients. The scatterplot above shows the heights of the male patients seen by the office at various ages less than 10 years. A linear model best describes the data, and the line of best fit is shown. For the patient that is exactly 8 years old, which of the following best estimates the percent increase from his actual height to the height that the model predicts?

• A. 20%
• B. 25%
• C. 75%
• D. 80%

Correct Answer: B

Explanation:

B

The question asks for the percent increase from a patient's actual height to that predicted by the line of best fit. Percent change is defined as . The child who is exactly 8 years old is 40 inches tall, and the line of best fit indicates that someone with an age of 8 will have a height of 50 inches. The difference in heights is 50 - 40 = 10 inches. Because the question asks for a percent increase, use the smaller number as the original. The percent change is = 25%. The correct answer is (B).