Question

The radius of a circle is decreasing at a rate of 2cm/ sec. What is the rate of change of the area of the circle with respect to time ( in cm^2/ sec).
A) -4pi r B) -2 pi r C) 2 D) 2 pi r or E) 4pi r

Answer 1

E) 4pi r

Answer 2

a'= 2*2 pi dr/dt ?

Answer 3

2 pi r dr/dt

dr/dt = 2

4 pi r

Answer 4

alrity thank you :)