Which one of (a), (b), (c), (d) or (e) is the odd one out and why?

odd one out

Source: based on a puzzle from Alex Bellos

  • $\begingroup$ Who downvoted? This is not bad for a small puzzle, in my opinion. $\endgroup$
    – oAlt
    May 4, 2020 at 12:20
  • 1
    $\begingroup$ @oAlt (Not me, but) we had a puzzle very similar to this, in that it had the same not-the-odd-one-out premise, not that long ago (a few weeks maybe?). I cannot find it now, it may have been deleted, but I recall it got a lot of flack, there was much discussion/debate in comments, and it garnered some downvotes. I wouldn't be surprised if this had a similar reception to some degree... $\endgroup$
    – Stiv
    May 4, 2020 at 12:46
  • $\begingroup$ @stiv if you find that post please share a link here. I searched before posting but as you imagine it is difficult to find a duplicate of this one $\endgroup$
    – melfnt
    May 4, 2020 at 13:05
  • $\begingroup$ @Stiv I see. (Why do I not remember that puzzle?) Anyway, in the long run, I cannot force someone to change their opinion on a particular puzzle. :) $\endgroup$
    – oAlt
    May 4, 2020 at 13:22

2 Answers 2


I'm thinking it is



it itself is not an odd-one-out answer, though ironically, that makes it an odd-one-out as well. But hear me out on this one.

(a) is the only red number.
(b) is the only smaller-than-normal number.
(d) is the only number missing a segment.
(e) is the only one without a middle black segment.

I still don't know how to explain the title, though.

  • 2
    $\begingroup$ rot13(Va Nyrk Oryybf' jbeqf: Gur bqq bar bhg, vf gur bar gung vf abg gur bqq bar bhg.) $\endgroup$ May 4, 2020 at 12:00
  • $\begingroup$ :00 but @melfnt the title remains unresolved LOL (is it a typo?) $\endgroup$
    – oAlt
    May 4, 2020 at 12:03
  • $\begingroup$ As for the title: it is just... curious $\endgroup$
    – melfnt
    May 4, 2020 at 12:06
  • $\begingroup$ @melfnt I'll take that as a yes to my question :P $\endgroup$
    – oAlt
    May 4, 2020 at 12:07
  • $\begingroup$ So it's basically like the "What is the smallest uninteresting number?" question. $\endgroup$ May 4, 2020 at 20:06

The problem with these sort of puzzles is that there are many possible answers. A few possible ones include these.

Answer 1:



It is smaller than the others

Answer 2:



It is red

Answer 3:



It is not a fully written number

Answer 4:



There is no black within it

This is just the start of hundreds, if not thousands of possible answers. I don't know if it intentional but it may be a good idea to be a bit more specific in the type of differences that you are looking for.

  • 4
    $\begingroup$ I think your examples illustrate that @oAlt is onto something. $\endgroup$
    – Anon
    May 4, 2020 at 11:54
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    $\begingroup$ @Anon my point is that if you keep on digging, you will eventually find a reason that any of them is odd, tenfold! $\endgroup$ May 4, 2020 at 11:57
  • 1
    $\begingroup$ Sooo which one of (a), (b), (c), (d) or (e) is the odd one out? XD $\endgroup$
    – melfnt
    May 4, 2020 at 12:04
  • $\begingroup$ Well, as I say there are many different answers oAlt has a point well made, yes, but it is possible that the question is unanswerble $\endgroup$ May 4, 2020 at 12:20

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