Question

A $20cm$ long iron pipe has an exterior diameter of $25cm$. If the thickness of the pipe is $1cm$ ,find the internal curved surface area of the pipe

Answer 1

Height of pipe $=20cm$
External diameter $=25cm$
External radius $=\frac{25}{2}=12.5cm$
Internal diameter $=25-(1+1)$
$=23cm$
Internal radius $=\frac{23}{2}=11.5cm$

Therefore, Inner CSA of pipe $=2\pi \left(11.5\right)\left(20\right)$

$=2\times 3.14\times 11.5\times 20$

$=1444.4c{m}^2$