math
posted by Rav .
A spherical ball is being filled with air. When the radius r=7cm, the radius is increasing at a rate 2 cm/s. How fast is the volume changing at this time (leave your answer approximate)?

V = (4/3)πr^3
dV/dt = 4πr^2 dr/dt
when r = 7 , dr/st = 2
dV/dt = 4π(49)(2) = 392π cm^3/sec
= appr 1231.5