\[S_{кв} = a^{2} = 3\ дм^{2} \Longrightarrow a = \sqrt{3}\ дм\]
\[S_{кв} = b^{2} = 75\ дм^{2} \Longrightarrow b =\]
\[= \sqrt{75} = 5\sqrt{3}\ дм\]
\[\frac{b}{a} = \frac{5\sqrt{3}}{\sqrt{3}} = 5\ \]
\[Ответ:\ \ в\ 5\ раз.\]