Answer
$\sqrt{0.5xy}$
Work Step by Step
Using $\sqrt{x}\cdot\sqrt{y}=\sqrt{xy}$ or the product rule of radicals, the given expression, $
\sqrt{0.1x}\cdot\sqrt{5y}
,$ is equivalent to
\begin{array}{l}\require{cancel}
\sqrt{0.1x(5y)}
\\\\=
\sqrt{0.5xy}
.\end{array}
