Question

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.

Answer 1

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. )