Wie rechne, von einem Preis, dem 20% hinzu gefügt wurden die 20% wieder ab um den Grundpreis zu bekommen?
$${\mathtt{500}}{euro}{\mathtt{\,\times\,}}{\mathtt{1.2}}{\mathtt{\,\times\,}}{\mathtt{0.8}} = {\mathtt{480}}{euro}$$
$${\mathtt{480}}{euro}{\mathtt{\,\times\,}}{\mathtt{1.041\: \!666\: \!66}} = {\mathtt{499.999\: \!996\: \!8}}{euro}$$
$${\mathtt{500}}{euro}{\mathtt{\,\times\,}}{\mathtt{1.2}}{\mathtt{\,\times\,}}{\mathtt{0.8}} = {\mathtt{480}}{euro}$$
$${\mathtt{480}}{euro}{\mathtt{\,\times\,}}{\mathtt{1.041\: \!666\: \!66}} = {\mathtt{499.999\: \!996\: \!8}}{euro}$$