Question

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

Answer 1

here,
height of well=20m
diameter=7m
therefore,radius=7/2m
volume of well=
$\pi ({r}^{2} )h$
22/7×7/2×7/2×20=770m^3
let the height of platform be h m
therefoer volume of platform=volume of earth
l×b×h=770
22×14×h=770
h=770/14×22
h=5/2=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.