Q. 93.8( 8 Votes )

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 (R^{2} – r^{2})h

= 3.14 × (22^{2} – 20^{2}) × 0.2

≈ 52 .8

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

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