$ \text{Gegeben:}\\\text{Breite} \qquad b \qquad [m] \\ \text{Länge} \qquad a \qquad [m] \\ \\ \text{Gesucht:} \\\text{Fläche} \qquad A \qquad [m^{2}] \\ \\ A = a\cdot b\\ \textbf{Gegeben:} \\ b=4m \qquad a=5m \qquad \\ \\ \textbf{Rechnung:} \\ A = a\cdot b \\ b=4m\\ a=5m\\ A = 5m\cdot 4m\\\\A=20m^{2} \\\\\\ \small \begin{array}{|l|} \hline b=\\ \hline 4 m \\ \hline 40 dm \\ \hline 400 cm \\ \hline 4\cdot 10^{3} mm \\ \hline 4\cdot 10^{6} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline a=\\ \hline 5 m \\ \hline 50 dm \\ \hline 500 cm \\ \hline 5\cdot 10^{3} mm \\ \hline 5\cdot 10^{6} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline A=\\ \hline 20 m^2 \\ \hline 2\cdot 10^{3} dm^2 \\ \hline 2\cdot 10^{5} cm^2 \\ \hline 2\cdot 10^{7} mm^2 \\ \hline \frac{1}{5} a \\ \hline 0,002 ha \\ \hline \end{array}$