Der Flächeninhalt$A\backslash \; A$ des Dreiecks$PQR\backslash \; PQR$ soll $99$ $c{m}^{2}cm^2$ sein.

$22$ Kästchen$\widehat{=}1cm\Rightarrow \overline{PQ}=6cm\backslash \; \backslash widehat\{=\}\backslash \; 1\backslash \; cm\backslash Rightarrow\backslash overline\{PQ\}=6\backslash \; cm$

$A_{PQR}={\displaystyle \frac{\overline{PQ}\cdot \overline{QR}}{2}}\Rightarrow \overline{QR}={\displaystyle \frac{2\cdot A_{PQR}}{\overline{PQ}}}\backslash \; A\_\{PQR\}=\backslash dfrac\{\backslash overline\{PQ\}\backslash cdot\backslash overline\{QR\}\}\{2\}\backslash Rightarrow\backslash overline\{QR\}=\backslash dfrac\{2\backslash cdot\; A\_\{PQR\}\}\{\backslash overline\{PQ\}\}$

$\overline{QR}={\displaystyle \frac{2\cdot 9c{m}^2}{6cm}}\Rightarrow \overline{QR}=3cm\backslash \; \backslash overline\{QR\}=\backslash dfrac\{2\backslash cdot\; 9\backslash \; cm^2\}\{6\backslash \; cm\}\backslash Rightarrow\backslash overline\{QR\}=3\backslash \; cm$.

Ergänze jetzt die Zeichnung zum Dreieck $PQRPQR$.

Die Zeichnung ist nicht maßtreu.