Answers by visitors named: Ehikioya

r=5cm; dr/dt=0.2cm/s Area of Circle, A=πr² Required to find: Increase in area=dA/dt dA/dt= (dA/dr) x (dr/dt) But dA/dr=2πr Hence, dA/dt=(2πr) x (0.2) =0.4πr Since r=5cm, dA/dt=0.4π x 5 =2π cm²/s