A well with inner radius 4 m is dug 14 m deep. Earth taken out of it has been spread evenly all around a width of 3 m it to form an embankment. Find the height of the embankment.
Let the height of the embankment be ‘h’ m
Radius of well = 4 m
Height of the well = 14m
Volume of earth dug out (volume of cylinder)
= 704 m3
Outer Radius of the embankment(R) = 4 m + 3 m = 7 m
Inner radius of the embankment(r) = 4 m
Volume of embankment =Volume of earth dug out
Volume of embankment 
= πh (R2 – r2)
= πh (72 – 42 )
= 33πh
Volume of embankment = Volume of earth dug out
⇒ 33πh = 704
⇒ h = 6.78 m
40