Question

a 20m deep Pit with diameter 7m is dug up and the earth from digging is spread evenly to form a platform 22m * 14m. the height of the platform is

Answer 1

Basically the logic is that the Volume of the mud dug will be same as that of the platform created
A platform has the following dimensions
l * b * h two of which are given
22*14*h is the Volume of the platform
Volume of the cylindrical hole of mud is = pi r²* h
= 22/7 * 7/2 * 7/2 * 20
= 11* 7 * 10
now
22 * 14 * h = 11*7*10
h= 10/4 or 2.5 m

Answer 2

⇒ Given:- Height (h) of pit :- 20m

Diameter (d) :- 7 m

Radius (r) :- 7/2 m

Volume of earth platform :- 22 m by 14m

⇒ To find :- Height of the platform:- ?

⇒ Solution:-

Volume of cylinder of radius 7/2 m and height 20 m

Volume of cylinder :- π(r^2)(h)

= 22/7×(7/2^2)×20 m^3

= 770 m^3

Let the height raised by 22 m × 14 m platform be equal to h metres

Therefore,

Volume of the earth in platform = Volume of the earth taken out of the pit

22 × 14 × h = 770

h = 770/22 × 14 m

h = 5/2 m

h = 2.5 m

Hence , the height of the platform is 2.5 m.