$\begin{array}{l} \text{Gegeben:}\\ \text{Radius} \qquad r \qquad [m] \\ \text{Kreiszahl} \qquad \pi \qquad [] \\ \\ \text{Gesucht:} \\\text{Oberfläche} \qquad O \qquad [m^{2}] \\ \\ O = 4\cdot r^{2} \cdot \pi\\ \textbf{Gegeben:} \\ r=1\frac{2}{5}m \qquad \pi=3\frac{16}{113} \qquad \\ \\ \textbf{Rechnung:} \\ O = 4\cdot r^{2} \cdot \pi \\ r=1\frac{2}{5}m\\ \pi=3\frac{16}{113}\\ O = 4\cdot (1\frac{2}{5}m)^{2} \cdot 3\frac{16}{113}\\\\O=24,6m^{2} \\\\\\ \small \begin{array}{|l|} \hline r=\\ \hline 1\frac{2}{5} m \\ \hline 14 dm \\ \hline 140 cm \\ \hline 1,4\cdot 10^{3} mm \\ \hline 1,4\cdot 10^{6} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline O=\\ \hline 24,6 m^2 \\ \hline 2,46\cdot 10^{3} dm^2 \\ \hline 2,46\cdot 10^{5} cm^2 \\ \hline 24630086\frac{96}{125} mm^2 \\ \hline 0,246 a \\ \hline 0,00246 ha \\ \hline \end{array} \end{array}$