SAT Math Multiple Choice Question 759: Answer and Explanation

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Question: 759

9. Images

Based on the ordered pairs in the table above, which of the following could express the relationship between the variables x and y?

  • A. y varies linearly with, but not directly as, x.
  • B. y varies directly as x.
  • C. y varies inversely as x.
  • D. y varies exponentially as x.

Correct Answer: C



Advanced Mathematics (variation) MEDIUM

To answer this question, it helps to be familiar with the concepts we discussed in Chapter 8, Lesson 4. The first thing to notice about the ordered pairs is that as the value of x increases, the value of y decreases. More specifically, notice that the product of the two values in each ordered pair is always the same: (2)(10) = 20, (4)(5) = 20, and (10)(2) = 20. A discussed in Chapter 8, Lesson 4, this is the hallmark of an inverse variation. The equation for this particular relationship is y = 20/x.

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