...which is funny (the Asterix thing), because spoken French isn't exactly brilliant with numbers either: 99 for example is expressed as "eighty nineteen", 70 as "sixty ten".
My friends lived in France a while and said their landlady could never count their rent (paid in cash) correctly first time. Always stumbled somewhere between 100x+60 and 100x+100 for integer values of x.
> 99 for example is expressed as "eighty nineteen"
Actually it's four-twenty-ten-nine (quatre vingt dix neuf) --
-- which is perfectly logical on a twenty-based numbering system. Of course it's not very helpful that they switched to ten-based, but only up to 60.
Same thing with Belgian French, much to my dismay.
I speak a language that does this as well (Georgian), where say 54 is ormotsdatotxmeti (two times twenty and fourteen.)
I didn't find maths particularly different difficulty wise, when thinking about it in Georgian or not. What did trip me up, was the times! Up to x:29 it's 29 minutes past x, but at x:30 it is 30 minutes to ++x. Weird.
It survives in part in quite a few other languages as well. E.g. Danish ("fjerds" is a contraction of "four into 20" = 80).
Most other European languages at least (I'm sure it's present elsewhere too, but I don't know enough non-European languages to say) have some remnants of more widespread counting in 12's or 20's or both (e.g. in English a "dozen" is 12, a "gross" is a dozen dozen (144), and a "score" is 20, hence "four score and seven years ago" in Lincolns Gettysburg Address - 87 years).
73 is soixante treize and is just this : a word (ok, two) one learns by heart. No French think that this is 60+13, but just 73.
I understand the point about logics in counting, but this is just a new word to learn, like déposition or balafré. One can analyze these words from an ethymology perspective but normally you just learn them by heart.
At least this is what I do in English when I need to remember went or throughout .
My friends lived in France a while and said their landlady could never count their rent (paid in cash) correctly first time. Always stumbled somewhere between 100x+60 and 100x+100 for integer values of x.
The Swiss have corrected this in Swiss French.