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Question
A path 2m wide surrounds a circular pond of diameter 40m. how many cubic meters of gravel are required to grave the path to a depth of 20cm ?
Solution
Diameter of circular pond = 40 m
Radius of pond(r) = 20m.
Thickness = 2m
Depth = 20cm = 0 2m
Since it is viewed as a hollow cylinder
Thickness (t) = R - r
2 = R - r
2 = R - 20
R = 22m
∴Volume of hollow cylinder = π(R2 - r2)h
= π(222 - 202)h
= π(222 - 202) x 0.2
= π(84) x 0.2
∴ Volume of hollow cylinder = 52.πm3
∴ 52.77m3 of gravel is required to
have path to a depth of 20cm.
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