3. A cube of ice melts without changing shape at the uniform rate of 4 cm³/min. What is the rate of change of the surface area of the cube, in cm²/min, when the volume of the cube is 125 cm³?

 Let,

S = the length of the sides of a cube

A = the surface are of a cube = 6S²

V = the volume of a cube = S³

 The rate at which the ice melts is given by,

However,

 So,

 We are looking for the rate of change of the surface area of the cube, which is given by,

 When the volume of the cube is 125 cm³_, S = 5cm, and so