110.25 × 0.01 \, ÷ 0.0025 - 420.25 equals ?

Answer: Option A

Given expression,
$$=\sqrt{\frac{11025}{100}}\times \sqrt{\frac{1}{100}}÷$$    $$\sqrt{\frac{25}{10000}}-$$ $$\sqrt{\frac{42025}{100}}$$
$$\begin{array}{rl}& =\frac{105}{10}\times \frac{1}{10}÷\frac{5}{100}-\frac{205}{10}\\ & =\frac{105}{100}\times \frac{100}{5}-\frac{205}{10}\\ & =21-\frac{205}{10}\\ & =\frac{210-205}{10}\\ & =\frac{5}{10}\\ & =\frac{1}{2}\\ & =0.50\end{array}$$