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Home » (i) How many cubic metres of soil must be dug out to make a well 20 metres deep and 2 metres in diameter? (ii) If the inner curved surface of the well in part (i) above is to be plastered at the rate of Rs 50 per m2, find the cost of plastering.
(i) How many cubic metres of soil must be dug out to make a well 20 metres deep and 2 metres in diameter?
(ii) If the inner curved surface of the well in part (i) above is to be plastered at the rate of Rs 50 per m2, find the cost of plastering.
CBSE | Class 10 | Exercise 1 | maths | Maths | Mensuration | ML Aggarwal
(i) How many cubic metres of soil must be dug out to make a well 20 metres deep and 2 metres in diameter?
(ii) If the inner curved surface of the well in part (i) above is to be plastered at the rate of Rs 50 per m2, find the cost of plastering.

Solution:

(i) Given diameter of the well, d = 2 m

Radius, r = d/2 = 2/2 = 1 m

Depth of the well, h = 20 m

Volume of the well, V = r2h

= (22/7)×12×20

= 62.85 m3

Hence the amount of soil dug out to make the well is 62.85 m3.

(ii)Curved surface area of the well = 2rh

= 2×(22/7)×1×20

= 880/7 m2

Cost of plastering the well per m2 = Rs. 50

Total cost of plastering the well = 50×(880/7)

= Rs. 6285.71

Hence the total cost of plastering is Rs. 6285.71.

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