PSAT Math Multiple-Choice Question 421: Answer and Explanation

Question: 421

A biologist studying the birth rate of a certain fish uses the function b(n) to analyze the fish's effect on other parts of the ecosystem, where n is the number of eggs laid by the fish over a given period of time. Which of the following lists could represent the domain for the biologist's function?

• A. {... -1,500, -1,000, -500, 0, 500, 1,000, 1,500...}
• B. {-1,500, -1,000, -500, 0, 500, 1,000, 1,500}
• C. {0, 0.25, 0.5, 0.75, 1, 1.25, 1.5...}
• D. {0, 500, 1,000, 1,500, 2,000...}

Correct Answer: D

Explanation:

D

Difficulty: Easy

Getting to the Answer: The domain of a function represents the possible input values. In this function, the input values are represented by n, which is the number of eggs laid by the fish over a given period of time. Because there cannot be a negative number of eggs laid or a fraction of an egg laid, the list in (D) is the only one that could represent the function's domain.