Question

A circular tank of diameter 2 m is dug and the earth removed is spread uniformly all around the tank to form an embarkment 2 m in width and 1.6m in height find the depth of the circular tank.

Answer 1

For circular tank

external radius R = 3 m
internal radius r = 1 m

thus volume of embankment

V = pi (R^2 - r^2) * h
= pi (9-1) * 1.6
= 40.192 m^2

now volume of tank

V' = pi r^2 h
= 3.14 * 1 * h

since both are equal

V = V'
thus
3.14 h = 40.192
h = 12.8 m

thus depth of tank is 12.8 m

Hope this helps :)