Question

the chapter surface area and volume to class 10th and ask your question, a 20 m deep well with diameter 7m is dug and the earth from digging is evenly spread out to form a platform 20 m by 14 M find the height of the platform

Answer 1

Hello Mate!

So, the well is in cylindrical form in which,

Volume of cylinder = πr²h

Volume of cylinder = 22/7 × (7/2)² × 20 m³

Volume of cylinder = 22/7 × 7/2 × 7/2 × 20 m³

Volume of cylinder = 11 × 7 × 10 m² = 770 m³

Now this volume is spread in a cuboidal platform which will have same volume.

l × b × h = 770 m³

20 × 14 × h m² = 770 m³

h = 2.75 m

Hence height of platform is 2.75 m

Have great future ahead!

Answer 2

⇒ Given:- Height (h) of well :- 20m

Diameter (d) :- 7 m

Radius (r) :- 7/2 m

Volume of earth platform :- 20 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 20 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

20 × 14 × h = 770

h = 2.75 m

Hence , the height of the platform is 2.75 m.