In measuring the sides of a rectangle, one side is taken 20% in excess and the other 10% in deficit. Find the error per cent in area calculated from the measurement ?

A 8% excess

B 9% deficit

C 12% excess

D 11% deficit

Correct Answer: Option A

Since Area of Rectangle = side1 x side2
Therefore, error% in area
= \(x\;+\;y\;+\;\frac{xy}{100}\)%

= [20 - 10 + ( -10 x 20)/100]% or 8%
i.e. 8% excess.