Find the cost of plastering

A well has to be dug that is to be 22.5 m deep and of diameter 7 m. Find the cost of plastering the inner curved surface at Rs.4 per sq metre:

  1. Rs. 1690
  2. Rs. 1875
  3. Rs. 1980
  4. None of these
Anurag Mishra Professor Asked on 8th January 2016 in Maths.
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1 Answer(s)

Answer: (3) 1980

Explanation:-
The deep of the well = 22.5 m
The diameter of the well = 7 m
Therefore, the radius of the well = 7/2 = 3.5 cm

Then, the curved surface area of the well = 2 x 22 x 7 x 22.5/7 x 2
= 22.5 x 22
= 495 sq. m

The cost of plastering the inner curved surface at Rs.4 per sq meter
Then, the total cost of plastering the inner curved surface of the well = 495 x 4
= Rs. 1980.

Hence, the correct answer is option (3) Rs. 1980.

Anurag Mishra Professor Answered on 8th January 2016.
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