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Problem 10 - Entrance Test

A spherical balloon inflates so that its radius increases at 0.5 cm/s. When r = 6 cm, how fast is the volume increasing (in cm³/s)?

Correct: D

V = (4/3)πr³ → dV/dt = 4πr² dr/dt = 4π(6²)(0.5) = 72π cm³/s.