Q10 of 32 Page 13

A 20 m deep well with diameter 14 m is dug up and the earth from digging is evenly spread to form a platform 22 mx14 m. Find the height  of the platform.

Given, Depth of the well = 20 m
Diameter of the well = 14 m
hence radius of the well = 7 m
Earth taken out from the well = πr2h    
                                           = x (7)2 x 20
                                           = 3080 cm3
Volume of the platform = Volume of the earth
 Area of the base x height = 3080
                       22 x 14 x h = 3080
Hence                      h=10 m.

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