if dr/dt = .5 cm/s (given)
and at t=0 , r = 15
when t = 20
r = 15 + 20(.5) = 25 cm
A = πr^2
dA/dt = 2πr dr/dt
mπ = 2π(25)(.5)
m = 25
At time t=0 s, the radius of a circle is equal to 15 cm. The radius of the circle increases at a rate of 0.5 cm/s. The rate of change of area at t=20 s is equal to mπ cm^2/s, where m is a positive integer. What is the value of m?
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