Question

A hollow cylindrical pipe is 210 cm long. Its outer and inner diameters are 10 cm and 6 cm respectively. The volume of the copper used in making the pipe is

Answer 1

Given, outer radius (R) = $\frac{10}{2}=5cm$
Inner radius (r) = $\frac{6}{2}=3cm$

So, volume of copper used
= Outer volume - Inner volume

$=\pi R^{2}h-\pi r^{2}h$

$=\frac{22}{7}\times 5^2\times 210-\frac{22}{7}\times 3^2\times 210$

$=10560{cm}^3$