# Civil Engineering - UPSC Civil Service Exam Questions - Discussion

18.

A plot of land 60°m x 20 m is measure steel tape. If the standard error of length width measurements is taken as ± 1 cm, the standard error of the area of the plot be

 [A]. ± 0.1414 m2 [B]. ± 0.566 m2 [C]. ± 0.632 m2 [D]. ± 0.8484 m2

Explanation:

No answer description available for this question.

 Pranay said: (Sep 12, 2015) How? Please explain.

 Raj said: (Sep 20, 2015) standard error of A = ^,A = SQRT[(^,A/^,X)^2 ^,X^2+(^,A/^,Y)^2 ^,Y^2].

 Abhay said: (Feb 2, 2016) Std Error of A = σA = Sqrt{(δA/δX)2σX2+ (δA/δY)2σY2} A = X * Y. X = 60 +/- 0.01m , Y = 20m +/- 0.01m. Since [(δA/δX) = Y and (δA/δY) = X. Substituting value of X and Y with either +ve error or -ve error. σA = Sqrt{Y2*(0.01)2 + X2*(0.01)2} = +/- 0.6325.

 Rakesh said: (Dec 19, 2016) Please give correct explanation to understand the solution.

 Arpon said: (Oct 11, 2017) How ? can't understand. Please explain.

 Arpon said: (Oct 11, 2017) Here, error = √[ {(length)^2 * (error in length)^2} + {(width)^2 * (error in width)^2}].