\[\sqrt{\frac{2}{5}} + \sqrt{\frac{5}{2}} + \sqrt{10} =\]
\[= \frac{{\sqrt{2}}^{\backslash\sqrt{2}}}{\sqrt{5}} + \frac{{\sqrt{5}}^{\backslash\sqrt{5}}}{\sqrt{2}} + {\sqrt{10}}^{\backslash\sqrt{10}} =\]
\[= \frac{2 + 5 + 10}{\sqrt{10}} = \frac{17}{\sqrt{10}} =\]
\[= \frac{17\sqrt{10}}{10} = 1,7\sqrt{10}.\]