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

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In this question we have to find cubic meters of gravel
which is required to grave the path to a depth of 20cm,
given that,
A path 2 m wide surrounds a circular pond of diameter 40 m.

One of the important question for the board exam class 10 from
mensuration chapter.This question is from r d sharma class 10 maths.
chapter-16 question number-28 maths r d sharma,mensuration.

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1. Given,

Diameter of the circular pond = 40 m

So, the radius of the pond = 40/2 = 20 m = r

Thickness (width of the path) = 2 m

As the whole view of the pond looks like a hollow cylinder.

And the height will be 20 cm = 0.2 m

So,

Thickness (t) = R – r

2 = R – 20

R = 22 m

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

= π (222– 202) × 0.2

= 52.8 m3

Therefore, 52.8 cubic meters of gravel are required to grave the path to a depth of 20 cm.

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