calc I help..?!!!?

Question

a spherical snowball is melting. its radius is decreasing at 0.2 cm per hour when the radius is15 cm. How fast is its volume decreasing at that time?

Answer 1

V = (4/3)πr^3
dV/dt = (4πr^2)(dr/dt)
dV/dt = - (4π15^2)(0.2)
dV/dt ≈ - 565.4867 cm^3/h

Answer 2

sphere = (4/3) pi r 3 so when the radius decreases use the formula by putting (r-x)in place of (r) .'x' is nothing but the decrement of radius.and u can find the volume .
and off course volume doesn't depends on the speed .