$ \text{Gegeben:}\\\text{Fläche} \qquad A \qquad [m^{2}] \\ \\ \text{Gesucht:} \\\text{Seite} \qquad a \qquad [m] \\ \\ a = \sqrt{\frac{A\cdot 4}{\sqrt{3}}}\\ \textbf{Gegeben:} \\ A=\frac{1}{5}m^{2} \qquad \\ \\ \textbf{Rechnung:} \\ a = \sqrt{\frac{A\cdot 4}{\sqrt{3}}} \\ A=\frac{1}{5}m^{2}\\ a = \sqrt{\frac{\frac{1}{5}m^{2}\cdot 4}{\sqrt{3}}}\\\\a=0,68m \\\\\\ \small \begin{array}{|l|} \hline A=\\ \hline \frac{1}{5} m^2 \\ \hline 20 dm^2 \\ \hline 2\cdot 10^{3} cm^2 \\ \hline 2\cdot 10^{5} mm^2 \\ \hline 0,002 a \\ \hline 2\cdot 10^{-5} ha \\ \hline \end{array} \small \begin{array}{|l|} \hline a=\\ \hline 0,68 m \\ \hline 6,8 dm \\ \hline 68 cm \\ \hline 680 mm \\ \hline 6,8\cdot 10^{5} \mu m \\ \hline \end{array}$