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.
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.