Question

The radius of a circle is increasing at a rate of 3 ft/min. If the radius is 0 when the time is 0, how fast is the circle's area changing when time is at 10 minutes?

Answer 1

dr/dt = 3
r = 3t + c
since r(0) = 0,
r = 3t

a = πr^2
da/dt = 2πr dr/dt
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