Just window shopping on the world wide Web and came across listings, as many no doubt have, where the sex is labelled with 1.0 for the males and 0.1 for the females...

Today this provoked a thought, and I don't know the answer...

Where do they come from? Why 1.0 for males and 0.1 for females and not vice versa?

Can these be stacked, for example, 2.5 means x2 males and x5 females? If yes, what if you have 11 females?