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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

    So, radius = 7/2 m

    Also, Depth (h) = 20 m

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

    ∴ Volume of Cylinder = π×r2×h

    = 22×7×5 m3

    Let the height of the platform = H

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

    π×r2×h = Area of platform × Height of the platform

    We know that the dimension of the platform is = 22×14

    So, Area of platform = 22×14 m2

    ∴ π×r2×h = 22×14×H

    ⇒ H = 2.5 m

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