alleryStart learning →A sphere's radius grows at 0.1 cm/s. At what rate does its surface area grow when r = 5 cm?
A10 pi cm^2/s
B5 pi cm^2/s
C2 pi cm^2/s
D4 pi cm^2/s
Answer & Solution
Correct answer: D. 4 pi cm^2/s
S = 4 pi r^2 gives dS/dt = 8 pi r dr/dt = 8 pi x 5 x 0.1 = 4 pi cm^2/s.
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