Even then, math was hard

From the Things I Did Not Know files, courtesy of Nvmeri Innvmeri:

The Romans had no negative numbers, and could express only a limited range of fractions with numeric symbols, principally the twelfths from 1/12 to 11/12. (The American pound has 16 ounces, but the Roman libra was divided into 12 unciae.) That means that while any properly-formed Roman number can be expressed in Arabic numbers, the converse is not true.

Since Wilson Pickett has been on my mind of late, I asked for a Roman equivalent of 99½, which comes back XCIX S; apparently one through five twelfths are represented by horizontal lines ordered in pairs, and seven through eleven by S plus those same lines, so 999/12 would be XCIX S= – or something like that.



  1. Michael Hendry »

    30 June 2012 · 3:03 pm

    Yes. I probably should have mentioned that the Latin word for half is semis, which has some obvious English cognates. Thanks for the link.

  2. Rita »

    1 July 2012 · 6:42 pm

    But then they did, didn’t they? The Romans, I mean. They had to understand negative, otherwise how do you explain IX, IV, I-anything.

  3. CGHill »

    1 July 2012 · 9:32 pm

    I’m guessing that since they didn’t have a formal zero, it didn’t occur to them to subtract anything from it.

  4. Barks in the Country »

    6 July 2012 · 9:56 am

    Show off by doing some long division in Roman numerals.

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