math
posted by jj on .
a boy is blowing a spherical balloon at a rate of 50 cm3/s.at what rate is the radius of the balloon changing when the radius is 10 cm?give your answer to 2 decimal places.

dV/dt = 50 cm^3/s
V = (4/3)πr^3
dV/dt = 4πr^2 dr/dt
so when r = 10
50 = 4π(100) dr/dt
dr/dt = 1/(8π) cm/s = ... you do the button pushing,
(no calculator needed up to this point. )