What rate is the plate's area increasing?

Question

when a circular plate of metal is heated in an oven, its radius increases at a rate of 0.02 cm / min. At what rateis the plate's area increasing when the radius is 50 cm?

Answer 1

P = πr²

dP/dt = 2πr(dr/dt)

dP/dt = 2π(50)(0.02)