Question

A hollow cylindrical pipe is made up of copper and is 210 cm long. The outer and inner radii of the pipe are 10 cm and 6 cm respectively. Find the volume of copper used in making the pipe.

• A. $42,140{\text{cm}}^3$
• B. $42,240{\text{cm}}^3$
• C. $42,440{\text{cm}}^3$
• D. $42,340{\text{cm}}^3$

Answer 1

The correct option is B

$42,240{\text{cm}}^3$

External radius (R) = 10 cm

Internal radius (r) = 6 cm

Volume of copper used in making the pipe.

= Volume of external cylinder - Volume of internal cylinder

$=\pi R^{2}H-\pi r^{2}H$

$=\pi H(R^2-r^2)$

$=\frac{22}{7}\times 210\left[\right(10{)}^2-\left(6{)}^2\right]$

$=22\times 30\times (10+6)(10-6)$

$=660\times 16\times 4$

$=42,240{\text{cm}}^3$