So there is a system of writing mixed numbers (that is, a combination of whole number and fraction, used instead of an “improper” fraction) used in cases where typing vulgar fractions (e.g. ½) is difficult or impossible, wherein the whole number is joined to the fraction (written with full-size numbers separated by a forward slash) by a hyphen. For example, the quantity 1.5 is written as 1-1/2 when 1½ is desired but the ½ character is unavailable.

I think it is fair to say that this is a stupid, ambiguous, and terrible practice. Most would read 1-1/2 as 1 − ½, that is the expression one minus one-half. But nevertheless, I have seen it used; cf. this RPG Stack Exchange question about it, since the Pathfinder Roleplaying Game System uses it (and they inherited it from Dungeons & Dragons, at least the System Reference Document for the 3.5 edition of the game).

Does anyone know where this notation came from, who its proponents are, etc.? I realize this is a rather unusual question for this site, but I feel that the Stack Exchange system is ideal for this sort of question and that this site seems like the most likely Stack to include experts who might know the answer to this.

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    $\begingroup$ Well, if you think about it, the notation is actually not bad. Without a way to type $1 \frac{1}{2}$ with the ease of LATEX (a.k.a. MathJax) formatting, using a hyphen effectively separates unit from fraction. Personally, I would interpret 1-1/2 as "one and one-half" and 1 - 1 / 2 as "one minus one-half." But that's just me. $\endgroup$ – K. Jiang May 17 '16 at 3:55
  • $\begingroup$ @K.Jiang You could just spell it out, or use decimals, or use a space, and none of these would have the ambiguity that this does. $\endgroup$ – KRyan May 17 '16 at 11:56
  • $\begingroup$ I agree that this is not an optimal way of dealing with mixed numbers. This is why we usually avoid them altogether and use, as you have mentioned, decimals and the such. But an even more useful stragegy is to always use improper fractions. They are very effective, as 1-1/2 may be ambiguous, but there is no doubt about what 3 / 2 represents. $\endgroup$ – K. Jiang May 17 '16 at 13:32
  • $\begingroup$ @K.Jiang Yes, but years of elementary schools (at least in the US) teaching that this is, well, “improper” has led to a lot of non-academic publishers seeing it as poor form. Though it’s also worth noting that both of the examples I have here really have no excuse, being websites with the easily available ½ that I used in this very question. Nonetheless, I truly doubt that Wizards of the Coast invented this notation for D&D, hence the question. $\endgroup$ – KRyan May 17 '16 at 13:48
  • $\begingroup$ As a teacher I would rather use the simpler mathematical notation: 1+1/2 Regards. $\endgroup$ – Furia Jul 17 '18 at 2:04

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