Question

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

 

Answer 1

\[\text{ Let the length of the cylinder pipe be h = 21, dm = 210 cm } . \]
\[ \text{ Let the outer and the inner radius of the pipe be R cm and r cm, respectively } . \]
\[ \therefore 2R = 10\text{  and 2r } = 6\]
\[R = 5 \text{ cm and r = 3cm } \]
\[\text{ Volume of the copper used in making the pipe } , V = \pi\left( R^2 - r^2 \right)h\]
\[ = \frac{22}{7} \times \left( 5^2 - 3^2 \right) \times 210\]
\[ = 22 \times \left( 25 - 9 \right) \times 30\]
\[ = 22 \times 16 \times 30\]
\[ = 10560 {\text{ cm } }^3\]