The radius of a circle is increasing at 5cm/sec. Find the rate of change of the area when r=10cm

Answer 1

Area of a circle = pi*r² = A

dA/dt = 2*pi*r*dr/dt

if r = 10cm and dr/dt = +5 cm/sec dA/dt = 2*pi*(10)*(5) = 100*pi or 314.16 cm²/sec