Question

A hollow garden roller of 42 cm diameter and length 152 cm is made of cast iron 2 cm thick. Find the volume of iron used in the roller.

Answer 1

Diameter of the hollow garden roller = 42 cm

∴ Inner radius = `42/2` = 21 cm  ...`[∵ "Radius" = ("Diameter")/2]`

∴ Thickness of cast iron = 2 cm

∴ Outer radius = 21 + 2 = 23 cm

Volume of hollow cylinder = π(R² – r²) × h  ...[Where, R is outer-radius and r is inner-radius]

= `22/7 xx [(23)^2 - (21)^2] xx 152`

= `22/7 xx (529 - 441) xx 152`

= `22/7 xx 88 xx 152`

= `(22 xx 88 xx 152)/7`

= `294272/7`

= 42038.85 cm³