A well with 14m diameter is dug 8m deep. The earth taken out of it has been evenly spread all around it to a width of 21m to form an embankment. Find the height of the embankment.

Explanation

Volume of earth taken out`=pir^2h`
`=392pi`
radius of outer circle`=21+7=28m`
radius of inner circle`=7m`
Volume of embankment=Volume of earth taken out
`hpi(28^2-7^2)=392pi`
height of embankment=h`=0.533m`.