Question

A well of diameter 14m is dug 15m deep .The earth taken out of it has been spread evenly to form circular embankment all around the wall of width 7m . find the hieght of the embankment

Answer 1

r=d/2
r=7
volume of earth dug out =
$pi \times {r}^{2} \times height$
volume of dug out= volume of embankment(volume of hollow cylinder)
$pi \times {7}^{2} \times 15 = pi \times ( {outer \: radi}^{2} - {inner \: radi}^{2} ) \times heigh \: of \: embankment$
7^2×15=(7+7)^2-7^2)×h
49×15÷(14^2-7^2)×h
49×15/21×7=h
5m=h