A path 2 m wide surrounds a circular pond of diameter 40 m. How many cubic metres of gravel are required to grave the path to a depth of 20 cm?

Question

Philoid · Accepted Answer

Diameter of circular pond is given as 40 cm

∴ Radius of the pond, r = 20cm

Also, thickness, t = R – r

⇒ 2 = R – r

⇒ 2 = R – 20

⇒ R = 22cm

Volume of a hollow cylinder = π (R² – r²)h

= 3.14 × (22² – 20²) × 0.2

≈ 52 .8

∴ 52.8 cubic metres of gravel are required to grave the path to a depth of 20 cm