Find the approximate change in the volume of a cube of side x meters caused by increasing the side by 1%.
Given a cube whose side x is increased by 1%.
Let Δx be the change in the value of x.
Hence, we have
∴ Δx = 0.01x
The volume of a cube of radius x is given by
V = x3
On differentiating A with respect to x, we get
We know
Recall that if y = f(x) and Δx is a small increment in x, then the corresponding increment in y, Δy = f(x + Δx) – f(x), is approximately given as
Here, and Δx = 0.01x
⇒ ΔV = (3x2)(0.01x)
∴ ΔV = 0.03x3
Thus, the approximate change in the volume of the cube is 0.03x3 m3.