Compute the rate of change of volume of a cube given the rate of change of an edge

Given a cube with edges expanding at a rate of 1 centimeter per second, what is the rate of change of the volume of the cube when the length of an edge is:

5cm.
10cm.
$x$ cm.

First, we know the volume of a cube is given by

$V = e^3$

where $e$ is the length of an edge. Thus, the rate of change of the volume relative to the rate of change of an edge is given by

$\frac{dV}{de} = 3e^2.$

We use this formula to find the rate of change of the volume for given values of $e$ ,

If $e = 5$ then we have
$\frac{dV}{de} = 3 (5)^2 = 75 \text{ cm}^3 / \text{ sec}.$
If $e = 10$ then we have
$\frac{dV}{de} = 3(10)^2 = 300 \text{ cm}^3 / \text{ sec}.$
If $e = x$ then we have
$\frac{dV}{de} = 3 x^2 \text{ cm}^3 / \text{ sec}.$