The value of $$\sqrt {0.01} {\text{ + }}$$ $$\sqrt {0.81} {\text{ + }}$$ $$\sqrt {1.21} {\text{ + }}$$ $$\sqrt {0.0009} $$   is = ?

Given expression,
$$ = \sqrt {\frac{1}{{100}}} + \sqrt {\frac{{81}}{{100}}} + \sqrt {\frac{{121}}{{100}}} + $$      $$\sqrt {\frac{9}{{10000}}} $$
$$\eqalign{ & = \frac{1}{{10}} + \frac{9}{{10}} + \frac{{11}}{{10}} + \frac{3}{{100}} \cr & = 0.1 + 0.9 + 1.1 + 0.03 \cr & = 2.13 \cr} $$