Question

Help please
he radius r of a circle is increasing at a rate of 7 centimeters per minute.
(a) Find the rate of change of the area when r = 10 centimeters.

(b) Find the rate of change of the area when r = 30 centimeters.

Answer 1

A = pi r^2

dA/dt = 2pi r dr/dt

plug and chug

Answer 2

2*13.4*100=2680 right

Answer 3

you're given dr/dt = 7,

dA/dt = 2 pi*r * 7 = 14pi*r

Answer 4

(a) Find the rate of change of the area when r = 10 centimeters.

plugin r = 10

dA/dt = 14pi*10 = 140pi

Answer 5

similarly, see if u can do the part b)

Answer 6

14pi*30=420pi
right

Answer 7

Correct !

Answer 8

thank youuuu