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PSAT Math Multiple-Choice Practice Question 227

Question: 227

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 percent 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?

Correct Answer: D

Explanation:

D

Difficulty: Medium

Category: Problem Solving and Data Analysis/Functions

Getting to the Answer: 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). 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, (D), of the form y = a ยท (0.92)x.

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