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.

  5. Bayou Renaissance Man »

    23 July 2012 · 8:05 pm

    Around The Blogs…

    The ever interesting Dustbury has two links for us this week. One takes us to what the author calls an ‘Ancient Numbers Page’. If you’ve ever wanted to express 99 and nine-twelfths in Roman numerals, this site will do the conversion for you (and als…

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