The radius, r, of a circle is increasing at a rate of 4 centimeters per minute. Find the rates of change of the area when r = 8 centimeters. Answer is in (cm^2)/min.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
L e t r b e t h e r a d i u s o f t h e c i r c l e L e t t b e t h e t i m e r = 4 t r = 8 , 8 = 4 t t = 2 L e t A b e t h e a r e a o f t h e c i r c l e A = π r 2 S i n c e r = 4 t , A = 1 6 π t 2 d t d A = 3 2 π t S i n c e t h e r a i d u s i s 8 w h e n t h e t i m e i s 2 , 3 2 π ( 2 ) = 6 4 π T h e r e f o r e , t h e a n s w e r i s 6 4 π