# SAT Math Multiple Choice Question 259: Answer and Explanation

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**Question: 259**

**4.** A nutritionist is studying the effects of nutritional supplements on athletes. She uses the function Pi (a) to represent the results of her study, where a represents the number of athletes who participated in the study, and Pi represents the number of athletes who experienced increased performance while using the supplements over a given period of time. Which of the following lists could represent a portion of the domain for the nutritionist's function?

- A. {…-100, -75, -50, -25, 0, 25, 50, 75, 100…}
- B. {-100, -75, -50, -25, 0, 25, 50, 75, 100}
- C. {0, 2.5, 5, 7.5, 10, 12.5, 15…}
- D. {0, 15, 30, 45, 60, 75…}

**Correct Answer:** D

**Explanation:**

D

Difficulty: Medium

Category: Passport to Advanced Math / Functions

Strategic Advice: The domain of a function represents the possible values of x, or the input values. In this function, x is represented by a, which is the number of athletes who participated in the study.

Getting to the Answer: This is a real-world scenario, so you cannot simply use rules of functions to determine the domain. Because there cannot be a negative number of athletes or a fraction of an athlete, the list in (D) is the only one that could represent a portion of the function's domain.