Answer: 4π cm^2/minute
Step-by-step explanation:
Rate of change :
Change with respect to time (dr/dt)
dr/dt = 0.4cm^2/s
r = 5cm
The rate of change when the Radius is 5cm
Area / Circumference of a circle (A) = πr^2
From chain rule of differentiation:
dA/dt = (dr/dt) * (dA/dr)
If A = πr^2
dA/dr = 2πr
dA/dr = 2π * 5 = 10π
However,
dA/dt = (dr/dt) * (dA/dr)
dA/dt = (0.4) * (10π)
dA/dt = 4π cm^2/minute
