Question
A well with 10 m inside diameter is long 14 m deep. Earth taken out of it is spread all around it to a width of 5 m to form an embankment. Find the height of the embankment.
Solution
Radius of the wall
(r) =
(r) =
Depth of the wall (h) = 10 m Volume of the earth dug out = Volume of the well = π r2h = π(5)2(10) = 250π m3 Radius of the well with embankment (R)
= 5 + 5 = 10 m π Area of the embankment
= Area of the well with embankment
– Area of the well without embankment = πR2 – πr2 = π(R + r) (R – r)
= π(10 + 5) (10 – 5)
= 75π m2
∴ Height of the embankment
