The value of 0.160.4 is = ?

Answer: Option C

$$\begin{array}{rl}& =\sqrt{\frac{0.16}{0.4}}\\ & =\sqrt{\frac{0.16}{0.40}}\\ & =\sqrt{\frac{16}{40}}\\ & =\sqrt{\frac{4}{10}}\\ & =\sqrt{0.4}\\ & =0.63\end{array}$$