A well with 7 m inside diameter is dug 22.5 m deep and the earth taken out of it has been spread around it to a width of 10.5 m to form an embankment. Find the height of the embankment so formed.
Volume of the earth=πr2H where H is the depth of the well.
=227×3.52×22.5
=866.25cubic metre.
This earth is used to make the embankment.
Volume of earth(embankment)=πR2H−πr2h
⇒227×(10.5+3.5)2h−227×(3.5)2h=866.25
⇒227×14×14h−227×3.5×3.5h=866.25
⇒616h−38.5h=866.25 on simplification
⇒577.5h=866.25
⇒h=866.25577.5=1.5m
∴ The height of embankment=1.5m