Area of a healing wound

Question

The area of the healing one is given by A=pi*r^2. The radius is decreasing at a rate of 2 mm per day at the moment when r= 37. How fast is the area decreasing at the moment.

Answer 1

A = πr²

dA/dt = dA/dr x dr/dt

dA/dr = 2πr

dA/dt = 2πr dr/dt

Given : r = 37, dr/dt = -2

So you can find dA/dt now, and then ignore the negative sign here for the answer