If the radius of a sphere is increased by , by what percentage does its surface area increase?
Answer and explanation
Correct answer: C.
- Step 1: Surface area of a sphere of radius is , which depends on the square of the radius ().
- Step 2: When the radius increases by , the new radius is . The new surface area is . The increase is .
Answer
.
Why not the others: '' calculates linear ; '' uses an incorrect exponent; '' calculates an improper volumetric increment.
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