http://www.zum.de/Faecher/freiarb/niehaves/texte/uebersicht6.htm
http://www.frustfrei-lernen.de/mathematik/mathematik-6-klasse.html
http://aufgaben.bruchrechnen-kapiert.de/bruchrechner-kuerzen.php
$${\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{200}}}{{\mathtt{100}}}} = {\mathtt{6}}$$
$${\mathtt{r}} = {\frac{{\mathtt{2}}}{{\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\mathtt{\pi}}}}}} \Rightarrow {\mathtt{r}} = {\mathtt{1.365\: \!568\: \!126\: \!510\: \!591\: \!5}}$$