alleryStart learning →The radius of a circle grows at 2 cm/s. How fast is its area growing when the radius is 5 cm?
A10 pi cm^2/s
B25 pi cm^2/s
C20 pi cm^2/s
D5 pi cm^2/s
Answer & Solution
Correct answer: C. 20 pi cm^2/s
dA/dt = 2 pi r dr/dt = 2 pi x 5 x 2 = 20 pi cm^2/s.
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