A closed box with a square base of side x and height h has a volume of 32 cm3. Which expression gives its surface area in terms of x?
Answer and explanation
Correct answer: D. 2x^2 + 128/x
- Step 1: Volume x^2 h = 32, so h = 32/x^2. Step 2. Surface area = 2x^2 + 4xh = 2x^2 + 4x(32/x^2) = 2x^2 + 128/x. Answer: 2x^2 + 128/x. Why not the others: 2x^2 + 32/x: The side faces total 4xh = 4x(32/x^2) = 128/x. x^2 + 128/x: There are two square faces, top and bottom. 2x^2 + 4x: The height is not x.
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