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 × 2w. So, 128 = 2w2. Divide by 2 to get 64 = w2. 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.

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