A spherical snowball is melting in such a way that its diameter is decreasing at rate of 0.4 cm/min. At what rate is the volume of the snowball decreasing when the diameter is 8 cm. (Note the answer is a positive number).

Answer 1

v = 4π/3 r³
dv/dt = 4πr² dr/dt
= 4π*4² (-.4)
= -25.6π cm³/min

Answer 2

Rats. dr/dt = -.2, not -.4 (diameter d/dt)

So, take half of that answer.