Question

Calculus: Implicit differentiation and related rates.
Q. The area of a circular sinkhole increases at a rate of 420 square yards per day. How fast is the radius of the sinkhole growing when it's radius is 50 yards?

Answer 1

A = π r²
-> dA/dt = 2π r dr/dt
=> dr/dt = 420 / 2* 50 π = 1.34 yd/day