Civil Engineering - UPSC Civil Service Exam Questions - Discussion

44. 

A 20 m chain was found to be 10 cm too long after chaining a distance of 2000 m. It was found to be 18 cm too long at the end of the day's work after chaining a total distance of 4000 m. What is the true distance if the chain was correct before the commencement of the day's work ?

[A]. 3962 m
[B]. 4019 m
[C]. 3981 m
[D]. 4038 m

Answer: Option B

Explanation:

No answer description available for this question.

Parushrut said: (Jun 25, 2016)  
Please describe it.

Rahul Chopra said: (Sep 15, 2016)  
L = 20m
L' = 20 + {(0 + 0.10)/2} = 20.05 mean elongation.
Measured lngth = 2000m(M.L).
True length(T.L) = L'/L * M.L.
T.L = 20.05/20 * 2000.
= 2005m.

2nd part
2nd M.L = 4000 - 2000 = 2000m.
mean elongation for part 2nd = 20{(.10 + .18)/2} = 20.14.

T.L = 20.14/20 * 2000(2nd M.L).
= 2014m.

Therefore, the True distance = 2005 + 2014 = (part1 + part2) = 4019m.

Rahul Guleria said: (Apr 2, 2017)  
T*T' = F' * F.

F' = 20(.10+.18/2) = 20.14,
Now T * 20 = 20.14 * 4000.

T = 20.14 * 4000/20 = 4029.
So the answer is B.

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