Question

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

Answer 1

volume of well= π*r*r*h
= 22÷7*3.5*3.5*20
=22*35
=770m^3

Now,volume of well= volume of platform
l=22m
b=14m
h= ?
therefore, l*b*h = 770 m^3
22*14*h= 770
22*h=55
h=55÷22--> h=2.5m

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.