An error 2% in excess is made while measuring the side of a square. The percentage of error in the calculated area of the square is:

Answer: Option D

100 cm is read as 102 cm.
∴ A₁ = (100 x 100) cm² and A₂ (102 x 102) cm²
(A₂ - A₁) = [(102)² - (100)²]
              = (102 + 100) x (102 - 100)
              = 404 cm²
∴ Percentage error
$$\begin{array}{rl}& =\left(\frac{404}{100\times 100}\times 100\right)\%\\ & =4.04\%\end{array}$$