# SAT Math Multiple Choice Practice Question 591: Answer and Explanation

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**Question: 591**

**5.** If *y* is directly proportional to the square of *x*, then which of the following tables could represent values of *x* and *y* ?

A.

B.

C.

D.

E.

**Correct Answer:** D

**Explanation:**

**D** The term *direct proportion* means that once you square *x*, the ratio between *x*^{2} and *y* should be the same for all pairs in the table. Use your test booklet as scratch paper and write the value for *x*^{2} for each pair to check the ratios. In A, 2^{2} = 4, for a ratio of 1 : 4. This does not match the 9 : 6 ratio of the next pair, so eliminate A. The first ratio in B is 1 : 2, but the second is 16 : 8, so eliminate B. In C the first ratio is 4 : 3, but the second is 16 : 9, so eliminate C. Only D is a match: 1 : 3, 4 : 12, and 9 : 27 are all equivalent ratios.