Answer:
Step-by-step explanation:
a)area A=pi r^2
rate of change of area =dA/dt =2 pi r dr/dt
given dr/dt =25 ,r =50
rate of change of area =dA/dt =2 pi *50 *25 =2500pi=7854
area growing 7854 cm2/s
b)area A=pi r^2
rate of change of area =dA/dt =2 pi r dr/dt
given dr/dt =25 ,A =64
pi r^2 =64
=>r =8/√pi
rate of change of area =dA/dt =2 pi *(8/√pi) *25 =400√pi=708.98
area growing 708.98 cm2/s
