The radius of the circle, in cm, after t seconds would be 50t
The area, A, of the circle after t seconds is expressed in the equation: A = pi r^2
A = pi (50T)^2 = pi2500t^2
The change of area per unit time is obtained by differentiating the equation
A' = pi25002t A' = pi5000t
when t = 3 secondsA' = pi5000*3 = 47122 cm2/s