Question

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?
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Answer 1

Answer:

16.8 π

Step-by-step explanation:

Area of the path = π (40/2 + 2 )² - π (40/2)² = 84 π m²

amount of gravel needed = area * depth = 84 π m² * 0.20 m

= 16.8 π

Answer 2

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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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