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A spherical balloon's radius grows at 1 cm/s. Its surface area increases at what rate when the radius is 10 cm?
A40π cm^2/s
B160π cm^2/s
C80π cm^2/s
D20π cm^2/s
Answer & Solution
Correct answer: C. 80π cm^2/s
S = 4πr^2 gives dS/dt = 8πr(dr/dt) = 8π(10)(1) = 80π.
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