Question

A metal pipe has an external diameter of 4 cm and internal diameter of 3 cm and is 20 cm long then the volume of the metal used is

• A. $22$ $c{m}^3$
• B. $110$ $c{m}^3$
• C. $220$ $c{m}^3$
• D. $440$ $c{m}^3$

Answer 1

Answer: (B)

$110$ $c{m}^3$

Given A metal pipe an external diameter of 4 cm and internal diameter of 3 cm

Then metal pipe an external radius of 2 cm and internal radius of 1.5 cm

Then external volume of metal pipe=$\pi r^{2}h=\pi \times (2{)}^2\times 20=\pi \times 4\times 20=80\pi$

And internal volume of metal pipe=$\pi r^{2}h=\pi \times (1.5{)}^2\times 20=\pi \times 2.25\times 20=45\pi$

Then volume of metal used=$80\pi -45\pi =35\pi =35\times \frac{22}{7}=110c{m}^3$