Radius of well, ‘r’ = 3.5 m.
Height of well, h = 20 m.
(i) Volume of soil dug out of well, V = πr2h(∵ cylinder sphere)
= 770m3
(ii) Length of platform, l = 22 m.
Breadth, b = 14 m.
Height, h = ?
Volume of Platform, V= l × b × h (∵ Cuboid)
= 22 × 14 × h
∴ Volume of Platform = Volume of soil dug out of well.
∴ Height of platform is 2.5 m