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

Given,

Length of cylinder = 21 dm = 210 cm

Outer diameter = 10 cm

Outer radius = R = \(\frac{10}{2}\) = 5 cm

Inner diameter = 6 cm

Inner radius = r = \(\frac{6}{2}\) = 3 cm

∴ Area of base = π(R² - r²) = π(25 - 9) = 16π cm²

Volume of cylinder = area of base x height = 16π x 210 = 16 x \(\frac{22}{7}\) x 210 = 10560 cm³