Berechne zuerst den Flächeninhalt eines Passfotos.

${\text{A}}_{\text{Passfoto}}=B\cdot L\Rightarrow {\text{A}}_{\text{Passfoto}}=3cm\cdot 4cm{\text{A}}_{\text{Passfoto}}=12c{m}^2\backslash text\{A\}\_\backslash text\{Passfoto\}\backslash \; =\backslash \; B\backslash cdot\; L\backslash qquad\backslash \; \backslash Rightarrow\backslash qquad\backslash text\{A\}\_\backslash text\{Passfoto\}\backslash \; =\backslash \; 3\backslash \; cm\backslash cdot\; 4\backslash \; cm\backslash \backslash \backslash text\{A\}\_\backslash text\{Passfoto\}\backslash \; =\backslash \; 12\backslash \; cm^2$

Berechne jetzt den Flächeninhalt des Plakates indem Du den Flächeninhalt eines Passfotos mit der Anzahl der Schülerinnen und Schüler multiplizierst.

${\text{A}}_{\text{Plakat}}={\text{A}}_{\text{Passfoto}}\cdot 30\Rightarrow {\text{A}}_{\text{Plakat}}=12c{m}^2\cdot 30{\text{A}}_{\text{Plakat}}=360c{m}^2\backslash text\{A\}\_\backslash text\{Plakat\}\backslash \; =\backslash \; \backslash text\{A\}\_\backslash text\{Passfoto\}\backslash cdot\; 30\backslash qquad\backslash \; \backslash Rightarrow\backslash qquad\; \backslash text\{A\}\_\backslash text\{Plakat\}\backslash \; =\backslash \; 12\backslash \; cm^2\backslash cdot\; 30\backslash \backslash \backslash text\{A\}\_\backslash text\{Plakat\}\backslash \; =\backslash \; 360\backslash \; cm^2$

Das Plakat muss mindestens einen Flächeninhalt von $360c{m}^{2}360\backslash \; cm^2$ haben, damit kein Passfoto überklebt wird.