What is the least number which should be subtracted 0.000326 in order to make it a perfect square = ?

Answer: Option A

$$\begin{array}{rl}& 0.000326=\frac{326}{{10}^6}\\ & 1|\overline{3}\overline{26}(18\\ & |1\\ & |------\\ & 28|226\\ & |224\\ & |------\\ & 2\end{array}$$
∴ Required number to be subtracted
$$\begin{array}{rl}& =\frac{2}{{10}^6}\\ & =0.000002\end{array}$$