NCERT Solution Class X Mathematics Surface Areas and Volumes Question 3 (Ex 13.3)

Question 3:

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.     [Use π = 22/7]

Answer:

The shape of the well will be cylindrical.

Depth (h) of well = 20 m

Radius (r) of circular end of well = 7/2 m

Area of platform = Length × Breadth = 22 × 14 m2

Let height of the platform = H

Volume of soil dug from the well will be equal to the volume of soil scattered on the platform.

Volume of soil from well = Volume of soil used to make such platform

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

Therefore, the height of such platform will be 2.5 m.

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