well, first off, you'd want to convert the decimal one to a fraction, we'll do so by notice that, it has two decimals, therefore, it'd be a fraction with two zeros at the bottom, and no dot above, let's do that,
[tex]\bf 1.\underline{25}\implies \cfrac{125}{1\underline{00}}\implies \stackrel{simplified}{\cfrac{5}{4}}[/tex]
now, what the units are, doesn't matter, ducks/geese, caymans/eels, or whatever else, so the rate is just the quotient of both values,
[tex]\bf \cfrac{1}{2}~~to~~\cfrac{5}{4}\implies \cfrac{\quad \frac{1}{2}\quad }{\frac{5}{4}}\implies \cfrac{1}{2}\cdot \cfrac{4}{5}\implies \cfrac{2}{5}\implies 0.4[/tex]
