Question

A metal pipe has an external radius of 4 cm and an internal radius of 3 cm The volume of the metal of length 10 cm is

• A. 120 $c{m}^2$
• B. 220 $c{m}^2$
• C. 440 $c{m}^2$
• D. 225 $c{m}^2$

Answer 1

The correct option is B 220 $c{m}^2$

Given that the external and internal radius of pipe is 4 cm and 3 cm and length is 10 cm

Then External volume of pipe =$\pi r^{2}h=2\pi (4{)}^2\times 10=\pi \times 16\times 10=160\pi$ sq cm

Or internal volume of pipe =$\pi r^{2}h=2\pi (3{)}^2\times 10=\pi \times 19\times 10=90\pi$ sq cm

Then volume of metal pipe=$160\pi -90\pi =70\pi =70\times \frac{22}{7}=220c{m}^2$