# SAT Math Multiple Choice Practice Question 504: Answer and Explanation

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**Question: 504**

**3.** The length of a certain rectangle is twice the width. If the area of the rectangle is 128, what is the length of the rectangle?

A. 4

B. 8

C. 16

D. 21

E. 42

**Correct Answer:** C

**Explanation:**

**C** Plug in the answers starting with C. If the length is 16, the width is half of that. 16 ÷ 2 = 8. Area is length × width. So, does 128 = 16 × 8? Yes, so C is correct. Alternatively, write an equation. The equation is area = *w* × 2*w*. So, 128 = 2*w*^{2}. Divide by 2 to get 64 = *w*^{2}. Take the square root of both sides to find *w* = 8. The length is twice this width, so length = 2 × 8 = 16, so the answer is C.