A spherical snowball is melting in such a way that its radius is decreasing

Question

A spherical snowball is melting in such a way that its radius is decreasing at a rate of 0.1 cm/min. At what rate is the volume of the snowball decreasing when the radius is 16 cm. (Note the answer is a positive number).

Answer 1

Let x be the diameter of the snow ball,

Diameter is decreasing at rate of 0.1 cm/min.=> dx/dt = -0.1

(decreaing is denoted with negative sign)

volume = =>

now = pi/2 * (16^2) * (-0.1) = -12.8* pi

the volume of the snowball decreasing when the diameter is 16 cm is

12.8 * pi or 40.21