$A=r^2\cdot \pi A=r^2\backslash cdot\backslash pi$

$r=\frac{d}{2}r=\backslash frac\{d\}\{2\}$

$r=60\text{ cm}r=60\backslash cm$

${\displaystyle \frac{3}{4}\cdot A=\frac{3}{4}\cdot ({60}^2\cdot \pi )=\mathrm{8482,30}}\backslash displaystyle\backslash frac\{3\}\{4\}\backslash cdot\; A=\backslash frac\{3\}\{4\}\backslash cdot(60^2\backslash cdot\backslash pi)=8482\{,\}30$

Die Größe der Sitzfläche beträgt $\mathrm{8482,30}c{m}^{2}8482\{,\}30\backslash \; cm^2$.

$U=2\cdot r\cdot \pi U=2\backslash cdot\; r\backslash cdot\backslash pi$

$U=2\cdot 60\cdot \pi U=2\backslash cdot60\backslash cdot\backslash pi$

${\displaystyle \frac{3}{4}\cdot U={\displaystyle \frac{3}{4}\cdot 120\cdot \pi =\mathrm{282,74}}}\backslash displaystyle\backslash frac\{3\}\{4\}\backslash cdot\; U=\backslash displaystyle\backslash frac\{3\}\{4\}\backslash cdot\; 120\backslash cdot\; \backslash pi=282\{,\}74$

$U_{gesamt}={\displaystyle \frac{3}{4}\cdot U+2\cdot r}U\_\{gesamt\}=\; \backslash displaystyle\backslash frac\{3\}\{4\}\backslash cdot\; U+\; 2\backslash cdot\; r$

$U_{gesamt}=\mathrm{282,6}+2\cdot 60=\mathrm{402,74}U\_\{gesamt\}=282\{,\}6+2\backslash cdot60=402\{,\}74$

Die Länge der Naht beträgt $\mathrm{402,74}\text{ cm}402\{,\}74\backslash cm$.

Richtiger Term:

$\frac{3}{4}\cdot \pi \cdot 2\cdot r+2\cdot r\backslash frac\{3\}\{4\}\backslash cdot\backslash pi\backslash cdot2\backslash cdot\; r+2\backslash cdot\; r$