Question

A hollow cylindrical pipe is $21cm$ long. If its outer and inner diameters are $10cm$ and $6cm$ respectively, them the volume of the metal used in making the pipe is $(Take\pi =\frac{22}{7})$

• A. $1048c{m}^3$
• B. $1056c{m}^3$
• C. $1060c{m}^3$
• D. $1064c{m}^3$

Answer 1

Answer: (B)

$1056c{m}^3$

The pipe is in the shape of a hollow cylinder.
Volume of a hollow Cylinder of outer Radius "R", inner Radius ""r" and height "h" $=\pi (R^2-r^2)h$
Outer Radius $=\frac{10}{2}=5cm$
Inner Radius $=\frac{6}{2}=3cm$
Hence, volume of the pipe $=\frac{22}{7}\times (5^2-3^2)\times 21=1056{cm}^3$