An iron pipe is 70 cm long. Its outer diameter is 14 cm and its inner diameter is 10 cm. What volume of iron is used in the pipe? Take $\pi = \frac{22}{7}$.

Explanation

1. 01

   Outer radius 7 cm, inner radius 5 cm.

2. 02

   Iron = $\pi (R^2 - r^2) h = \frac{22}{7} \times (49 - 25) \times 70$.

3. 03

   = $22 \times 24 \times 10 = 5{,}280$ cm³.