Q4 of 24 Page 145

How many m3 of soil has to be excavated from a rectangular well 28 m deep and whose base dimensions are 10 m and 8 m. Also, find the cost of plastering its vertical walls at the rate of ₹ 15/m2.

Given: Depth of a well = 28 m

Length = 10 m


Width = 8 m


Volume of a well = l × b × d


= 10 × 8 × 28


= 80 × 28


= 2240 m3


2240 m3 of soil has to be excavated from a rectangular well.


So, to calculate the cost of plastering.


Firstly we have to find the lateral surface of a rectangular well


Lateral Surface Area = 2h (l+b)


= 2 × 28 (10+8)


= 56 × 18


= 1008 m2


Cost of plastering per square metre = ₹ 15


Cost of plastering for 1008 m2 = ₹ 15 × 1008 = ₹15120


So, the cost of plastering the vertical walls of a rectangular well is ₹ 15120


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