Show that the relative error in computing the volume of a sphere, due to an error in measuring the radius, is approximately equal to three times the relative error in the radius.

Let the error in measuring the radius of a sphere be k%.


Let x be the radius of the sphere and Δx be the error in the value of x.


Hence, we have


Δx = 0.01kx


The volume of a sphere of radius x is given by



On differentiating V 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 = 0.01kx


ΔV = (4πx2)(0.01kx)


ΔV = 0.04kπx3


The percentage error is,




Error = 0.03k × 100%


Error = 3k%


Thus, the error in measuring the volume of the sphere is approximately three times the error in measuring its radius.


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