$\begin{array}{l} \text{Gegeben:}\\\text{Oberfläche} \qquad O \qquad [m^{2}] \\ \text{Kreiszahl} \qquad \pi \qquad [] \\ \\ \text{Gesucht:} \\ \text{Radius} \qquad r \qquad [m] \\ \\ r = \sqrt{\frac{ O}{\pi \cdot 4}}\\ \textbf{Gegeben:} \\ O=16\frac{1}{2}m^{2} \qquad \pi=3\frac{16}{113} \qquad \\ \\ \textbf{Rechnung:} \\ r = \sqrt{\frac{ O}{\pi \cdot 4}} \\ O=16\frac{1}{2}m^{2}\\ \pi=3\frac{16}{113}\\ r = \sqrt{\frac{ 16\frac{1}{2}m^{2}}{3\frac{16}{113} \cdot 4}}\\\\r=1,15m \\\\\\ \small \begin{array}{|l|} \hline O=\\ \hline 16\frac{1}{2} m^2 \\ \hline 1,65\cdot 10^{3} dm^2 \\ \hline 1,65\cdot 10^{5} cm^2 \\ \hline 1,65\cdot 10^{7} mm^2 \\ \hline 0,165 a \\ \hline 0,00165 ha \\ \hline \end{array} \small \begin{array}{|l|} \hline r=\\ \hline 1,15 m \\ \hline 11,5 dm \\ \hline 115 cm \\ \hline 1,15\cdot 10^{3} mm \\ \hline 1,15\cdot 10^{6} \mu m \\ \hline \end{array} \end{array}$