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

The shape of the well is considered to be cylindrical as shown in the figure.
Given: Depth(h) of well = 20m
Radius(r) of circular end of well = 7/2 m
Area of platform = Length x Breadth = 22 × 14 m²
Assume height of the platform = H m
The volume of soil dug from the well will be equal to the volume of soil in platform.
Volume of soil from well = Volume of platform
⇒ πr²h = Area of platform x Height of platform
π × (7/2)² × 20 = 22 × 14 × H
H = (22/7) × (49/4) × 20 / (22 × 14)
H = 5/2 = 2.5 m
Hence, the height of such a platform will be 2.5 m.