PSAT Math Multiple-Choice Question 797: Answer and Explanation

Question: 797

Caitlin opens a checking account that earns no interest to set aside spending money for vacations. Each month she puts the same dollar amount, $50, into the account. Unfortunately, she does not expect to be able to take a vacation at any point in the foreseeable future. Which of the following best describes the relationship between the number of months and the total amount of money in the account?

• A. A linear relationship, with the line of the relationship having a negative slope
• B. A linear relationship, with the line of the relationship having a positive slope
• C. An exponentially increasing relationship
• D. An inverse exponential relationship

Correct Answer: B

Explanation:

(B) Each month, Caitlin adds $50, so the function will have a constant slope of 50. Because the slope is constant, the function is linear. The slope is positive 50, so the answer is choice (B). We know that the slope will be positive because the two variables are directly proportional: as time goes on, the amount of money in the account increases.