JAMB 1989 · UME · Q44

A cylindrical metal pipe 1 m long has an outer diameter of 7.2 cm and an inner diameter of 2.8 cm. Find the volume of metal used for the pipe.

Worked solution (try it first)

Halve the diameters: outer radius 3.6 cm, inner radius 1.4 cm.
The length is 1 m, which is 100 cm.
The metal is the ring times the length: $\pi(3.6^2 - 1.4^2) \times 100 = \pi(12.96 - 1.96) \times 100$ .
That is $11\pi \times 100 = 1100\pi\text{ cm}^3$ , option B.