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.

Explanation

Length of cylinder`=21dm=210cm`
Outer diameter`=10cm`
Outer radius, `R=10/2=5cm`
Inner diameter`=6cm`
Inner radius, `r=6/2=3cm`
`∴` Volume of copper used in making the pipe`=pi(R^2–r^2)h`
`=22/7(52–32)xx210`
`=22/7(25-9)xx210`
`=10560cm^3`
Hence, the volume of the copper us `10560cm^3`.