$${\frac{{\mathtt{3}}}{{\mathtt{5}}}}{\mathtt{\,\times\,}}{\mathtt{120}}{km} = {\mathtt{72}}{km}$$
120 * 3/5 = 72
$${\frac{{\mathtt{1}}}{{\mathtt{5}}}}{\mathtt{\,\times\,}}{\mathtt{120}}{km} = {\mathtt{24}}{km}$$ => $${\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{24}}{km} = {\mathtt{72}}{km}$$
$${\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{120}}}{{\mathtt{5}}}} = {\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{120}}}{{\mathtt{10}}}} = {\frac{{\mathtt{720}}}{{\mathtt{10}}}} = {\mathtt{72}}$$
Gruß radix !