Finding rate of change of a part of a usually 3D shape (e.g. radius):
Working:
dV/dt = 50 (given)
dr/dt = need to find
dr/dt = dV/dt x dr/dV
r = 3h (given)
h = r/3
V = 1/3πr2h
V = 1/3πr²(r/3)
V = 1/9πr³
dV/dr = 1/3πr²
dr/dt = 50 x 1/(1/3π(10)²) = 0.477 cm/s
dr/dt = 50 x 1/(1/3π(10)²) = 0.477 cm/s
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