$
\text{Gegeben:}\\\text{Kathete} \qquad b \qquad [m] \\
\text{Kathete} \qquad a \qquad [m] \\
\\ \text{Gesucht:} \\\text{Fläche} \qquad A \qquad [m^{2}] \\
\\ A = \frac{a\cdot b}{ 2}\\ \textbf{Gegeben:} \\ b=0,002m \qquad a=\frac{2}{5}m \qquad \\ \\ \textbf{Rechnung:} \\
A = \frac{a\cdot b}{ 2} \\
b=0,002m\\
a=\frac{2}{5}m\\
A = \frac{\frac{2}{5}m\cdot 0,002m}{ 2}\\\\A=0,0004m^{2}
\\\\\\ \small \begin{array}{|l|} \hline b=\\ \hline 0,002 m \\ \hline \frac{1}{50} dm \\ \hline \frac{1}{5} cm \\ \hline 2 mm \\ \hline 2\cdot 10^{3} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline a=\\ \hline \frac{2}{5} m \\ \hline 4 dm \\ \hline 40 cm \\ \hline 400 mm \\ \hline 4\cdot 10^{5} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline A=\\ \hline 0,0004 m^2 \\ \hline \frac{1}{25} dm^2 \\ \hline 4 cm^2 \\ \hline 400 mm^2 \\ \hline 4\cdot 10^{-6} a \\ \hline 4\cdot 10^{-8} ha \\ \hline \end{array}$