Let the radius of circle =r cm Area of circle with radius r is given by A=πr^2 Therefore, the rate of change of A with respect to t = dA/dt = 2πr.dr/dt = 2πr.3 = 6πr When r=10 cm, then dA/dt=6π.(10)=60π cm^2/s Hence, the area of circle is increasing at the rate of 60π cm^2/s.