Question

Question 4
A well of diameter 3 m is dug 14 m deep. The earth taken out of it has been spread evenly all around it in the shape of a circular ring of width 4 m to form an embankment. Find the height of the embankment.

Answer 1

Radius of well = 1.5 m, depth of well = 14 m, width of embankment = 4 m
Radius of circular embankment = 4 + 1.5 = 5.5 m
Volume of earth dug out
$=\pi r^{2}h$
$=\pi \times {1.5}^2\times 14$
$=31.5\pi m^3$
Area of top platform = (Area of bigger circle - Area of smaller circle)
$=\pi (R^2-r^2)$
$=\pi ({5.5}^2-{1.5}^2)$
$=28\pi$
$Height=\frac{Volume}{Area}$
$=\frac{31.5\pi }{28\pi }=1.125m$