Question

Question 3
A 20 m deep well with diameter 7 m is dug and the earth from digging is evenly spread out to form a platform 22 m by 14 m. Find the height of the platform.

Answer 1

Radius of well = 3.5 m, depth of well = 20 m
Dimensions of rectangular platform = 22 m $\times$ 14 m
Volume of earth dug out
$=\pi r^{2}h$
$=\pi \times {3.5}^2\times 20$
$=22\times 35=770m^3$
Area of the platform = $22\times 14m^2$ (Area of rectangle=$l\times b$)
Let the height of the platform be H m.
Volume of the platform = Volume of the earth dug out
$22\times 14\times H=22\times 35$
$H=\frac{35}{14}=2.5m$