Question

a hollow cylindrical pipe is 21 dm long . its outer and inner diameters are 10 cm and 6 cm respectively. find the volume of the copper used in making the pipe.

Answer 1

volume of the hollow cylindrical pipe =
$\pi \times length \: of \: the \: pipe \: \times ({ { \:outer \: radius}^{2} - { \:inner \: radius}^{2}})$
=
$\pi \times 210 \times ( {5}^{2} - {3}^{2} )$
= 10555.75 cubiccm
~ 10.56 litres