# Hollow Circular Cylinder

Some examples of a hollow cylinder are pipes, circular buildings and bearing bushes. If is the outside radius of the cylinder and is the inside radius of the cylinder, then

(i)

(ii)

with and being the outer and inner diameter, and is volume.

__Example__**:**

A well with a **10m** inside diameter is dug **14m** deep. The earth taken out of it is spread all around to a width of **5m** to form an embankment. Find the height of the embankment.

__Solution__**:**

Volume of the dug out earth

Area of the embankment (shaded)

Height of the embankment

__Example__**:**

A hollow cylinder copper pipe is **21dm** long. Its outer and inner diameters are **10cm** and **6cm** respectively. Find the volume of the copper used in making the pipe.

__Solution__**:**

Given that:

The height of the cylindrical pipe is

External radius,

Internal radius,

Volume of the copper used in making the pipe

** **