Question

A 20m deep well with diameter 7m is dug out and earth from diffing is spread evenly to form a platform 22m *14 m find the height of platform

Answer 1

volume of earth dug=πr²h=22/7*7/2*7/2*20=770 m³

volume of platform=LBH=22*14*h m³(let h be the height of platform in metres)

volume of earth dug=volume of platform(since same soil which is dug is used to make platform)

770=22*14*h

⇒h=770/22*14

∴h=2.5 m

Answer 2

⇒ Given:- Height (h) of well :- 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 well

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.