A square plate is expanding uniformly, the side is increasing at the rate of 5cm/sec what is the rate at which the area and its perimeter is increasing when the side is 20 cm long?
Area, A = l2 ⇒dA/dt = 2l × dl/dt = 2 × 20 × 5
dA/dt = 200cm2/sec.
P = 41 ⇒ dP/dt = 4 dl/dt 4 × 5= 20cm/sec
