Question

An elastic spherical ballon is being blown up so that the radius is increasing at a rate of 1cm/sec. Calculate the rate at which the volume of the ballon is increasing when the radius is 5cm

Answer 1

v = 4π/3 r^3
dv/dt = 4π r^2 dr/dt
when r=5,

dv/dt = 4π * 25 * 1 = 100π cm^3/s