SAT Math Multiple Choice Question 578: Answer and Explanation

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Question: 578

8. One function of the Environmental Protection Agency (EPA) is to reduce air pollution. After implementing several pollution reduction programs in a certain city, EPA calculated that the air pollution should decrease by approximately 8% each year. What kind of function could be used to model the amount of air pollution in this city over the next several years, assuming no other significant changes?

  • A. A linear function
  • B. A quadratic function
  • C. A polynomial function
  • D. An exponential function

Correct Answer: D

Explanation:

D

Difficulty: Medium

Category: Problem Solving and Data Analysis / Functions

Strategic Advice: Determine whether the change in the amount of pollution is a common difference (linear function) or a common ratio (exponential function), or if it changes direction (quadratic or polynomial function).

Getting to the Answer: Each year, the amount of pollution should be 100 – 8 = 92% of the year before. You can write 92% as , which represents a common ratio from one year to the next. This means that the best model is an exponential function of the form y = a ? (0.92)x.

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