Question 436149
A stone is thrown into a pond. A circular ripple is spreading over the pond in
 such a way that the radius is increasing at the rate of 3. feet per second.
 Find a function, r(t), for the radius in terms of t.
:
r(t) = 3t
;
Find a function, A(r), for the area of the ripple in terms of r.
A(r) = {{{pi*r^2}}}
:
Find (A of r)(t).
A(rt) = {{{pi*(3r)^2}}}