Question

10. An iron pipe is 21 m long and its exterior diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weight is 8 g/cm3, find the weight of pipe.​

Answer 1

Outer diameter = 8cm

Outer radius = 8 ÷ 2 = 4cm

Outer volume = πr²h

$= \frac{22}{7} \times 4 \times 4 \times 21$

$= 1056 {cm}^{3}$

Inner diameter = 8 - 1 - 1 = 6cm

Outer radius = 6 ÷ 2 = 3cm

Outer volume = πr²h

$= \frac{22}{7} \times 3 \times 3 \times 21$

$= 594 {cm}^{3}$

Actual volume of pipe = 1056 - 594 = 462cm³

Weight = 462 × 8 = 3696g = 3.69 kg