5 ms·

I thought 9 was IX

• thaumasiotes 6y ago
  You're free to write it that way if you want, but that just adds an unnecessary step to doing math with it.
• dhosek 6y ago
  The prefix = subtraction convention came late in the history of Roman numerals. I think it might even postdate the introduction of Arabic numerals, but I can't say for sure since I'm going from memory here. If I were less lazy, I'd look at wikipedia which doubtless can give a more definitive answer.
  • thaumasiotes 6y ago
    Wikipedia has plenty of citations to classical Rome. Colosseum gate 44: XLIIII (not, for whatever reason, XLIV, or XXXXIIII) 18th legion: XIIX 22nd legion: IIXX There was evidently not a strict standard. (Note also that the symbols we use for high values, D and M, weren't really what the Romans used. You can see Roman abaci with columns labeled with place values: https://en.wikipedia.org/wiki/File:RomanAbacusRecon.jpg https://en.wikipedia.org/wiki/File:RomanAbacusRecon.jpg https://thatsmaths.com/2019/07/04/what-did-the-romans-ever-do-for-maths/ https://thatsmaths.com/2019/07/04/what-did-the-romans-ever-d... Those look the same; I don't know whether the one is a replica of the other or whether the form was just that standardized. But the columns are plainly labeled as, in ascending order, ϴ, I, X, C, ∞, ((|)), (((|))), and |X|. I speculate that ∞ is a fancy way of writing (|); I believe our M descends from Roman (|) and our D from Roman |). )