Explanation:

Let us assume the well is a solid right circular cylinder
Radius(r) of the cylinder =3.5/2 m =1.75 m
Height or depth of the well (h) = 16 m
Volume of the cylinder = ∏×r²×h
∏×1.75²×16 ……………………………………………………….(i)
Given,
The length of the platform (l) = 27.5 m
Breadth of the platform (b) =7 m
Let the height of the platform be x m
Volume of the rectangle = l*b*h
V = 25*5*x ……………………………………………………………………………………………(ii)
Since the well is spread evenly to form the platform
So equating equations (i) and (ii), we get .
V1 = V2
∏×1.75²×16 = 27.5*7*x
x = 0.8 m
Therefore x = 80 cm
The height of the platform is 80 cm.