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A 20 m 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. Q.3

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In chapter surface areas and volumes ncert class 10 of exercise 13.3 question no. 3 . Find the easiest and best solution of this question , its very important question of this chapter please help me to find out the easiest method of this question .A 20 m 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.

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1. It is given that the shape of the well is in the shape of a cylinder with a diameter of 7 m

Also, Depth (h) = 20 m

Volume of the earth dug out will be equal to the volume of the cylinder

âˆ´ Volume of Cylinder = Ï€Ã—r2Ã—h

= 22Ã—7Ã—5 m3

Let the height of the platform = H

Volume of soil from well (cylinder) = Volume of soil used to make such platform

Ï€Ã—r2Ã—h = Area of platform Ã— Height of the platform

We know that the dimension of the platform is = 22Ã—14

So, Area of platform = 22Ã—14 m2

âˆ´ Ï€Ã—r2Ã—h = 22Ã—14Ã—H

â‡’ H = 2.5 m

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