# SAT Math Multiple Choice Question 198: Answer and Explanation

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**Question: 198**

**3.** During the month of July, the number of units, y, of a certain product sold per day can be modeled by the function y = -3.65x + 915, where x is the average daily temperature in degrees Fahrenheit. Which of the following statements must be true?

- A. As the temperature increases, the number of units sold decreases.
- B. As the temperature increases, the number of units sold remains constant.
- C. As the temperature increases, the number of units sold increases.
- D. There is no linear relationship between temperature and the number of units sold.

**Correct Answer:** A

**Explanation:**

A Whenever there are variables in the question, think Plugging In. The answers refer to what happens when the temperature, x, increases, so plug in more than one value of x. Plug in x = 1 into the equation to get y = -3.65(1) + 915 = -3.65 + 915 = 911.35. Next plug in x = 2 to get y = -3.65(2) + 915 = -7.3 + 915 = 907.7. As average daily temperature, x, increased, the number of units sold, y, decreased. Therefore, the correct answer is (A).