It’s the Friday Puzzle!


I am speaking about the psychology of dreams at the British Science Festival 2012 in Aberdeen at the weekend.  Do come along and say hi.  Details here.

OK, here is the puzzle.  As ever, please do NOT post your answers, but do say if you think you have solved the puzzle and how long it took. Solution on Monday.

If you turn this number upside down or reflect it left-to-right you get 11 either way, but the original number is not 11.  What is it?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.


43 comments on “It’s the Friday Puzzle!

  1. Alex says:

    Quite quick to get an answer, whether it’s the right answer or not, will find out Monday!

  2. Roland says:

    Took me just a little less than 11 seconds (if my answer is right 😉 )

  3. Dave says:

    Cue sumg “Got it in less than X seconds” comments

  4. Anonymous says:

    2 answers, both correct in 2 seconds

  5. falsedog says:

    Embarrassed – nearly an hour to get this one :0s

  6. Anonymous says:

    I got an answer in 5 sec onds, whether that answer turns out to be correct…

  7. Hugh Janus says:

    There are 10 types of people on this planet – those that understand binary and those that do not

  8. The Masked Twit says:

    I guess it depends on the meaning or indeed meanings of “11”.

  9. Paul Durrant says:

    I got one answer and a dodgy second answer. Reading the comments gets a third.

  10. Hmmm got an answer I’m not happy with very quickly. Browsing the comments I see another I’m even less happy with. With recent track record, thinking the answers rubbish will certainly not discount it from being the one given on Monday.

  11. Julie says:

    Why is my answer so much more banoffe than binary ?

  12. Tom Cantwell says:

    There is only one answer and it’s much simpler than some of these comments would suggest.

  13. Martha says:

    I’ve got a good answer which is nothing to do with binary, and I don’t get the comments ’11’ in binary is 3, so what’s that got to do with anything?

  14. Al says:

    I have two answers. The first one, which I think is the one you will reveal on Monday only took a few seconds to get. The second answer I got after reading some of the comments – it is also correct given the way the question is phrased.

  15. Hilary says:

    About a nanosecond – before I’d finished reading the question, in fact. Always assuming I’m right, of course…..

  16. Anders says:

    It took me about 5 minutes, but I am not sure if it is right or not. It depends a little on what “turn it upside down” means. My answer doesn’t work if it means a mirror reflection, but if it means writing the answer on a piece of paper and turning it through 180 degrees it works

  17. Rachel Mills says:

    Thought about for a couple of minutes – couldn’t see the answer. Dozed, woke up and saw the answer straight away.

  18. Dipper says:

    Ah, Mr Wiseman, you are a rotter!! Took me about a minute – good one.

  19. mike hayward says:

    It took 4.3 seconds to come up w/an answer. It took a full minutesnd a half trouble convince myself the answer was too easy and that I have an 83.8% chance of being wrong.

  20. charm says:

    1 sec to find the answer……:)

  21. Gary Patterson says:

    Think I’ve got it; 3 false starts & then “ahhhhh”. About 5 min.

  22. Jerry996 says:

    I got an answer almost immediately. Whether it is correct or not will have to wait until Monday!

  23. Jerry996 says:

    The problem says “If you turn this number upside down or reflect it left-to-right you get 11 either way, but the original number is not 11. What is it?” Does Richard mean that the number in question is represented as “11” or that “11” is the number “eleven”?

    • Stupid Illiterite sociopath. says:

      My interpretation is that Richard’s first “11” means the integer between ten and twelve. The second “11” means the symbol “11”.
      There is another solution as well if you interpret the question differently. Again you have to ascribe two different meanings to the symbol “11” in the question to make it work.
      In other words it is a trick question.

    • Match says:

      It is the actual number eleven in both cases.

    • Stupid Illiterite sociopath. says:

      I see what you mean now Match.
      i now how three answers, with my third being the one I expect RW to post.
      The comment below about the clear wording of the question helped.
      My other two answers and my comments are still acceptable within the normal parameters of WisemanWorld.

  24. Anonymous says:

    Took me about 4 seconds to come up with an infinete amount of correct answers

  25. gjdv says:

    It took me about 4 seconds to come up with an infinite amount of correct answers

  26. Lazy T says:

    9 secs to get an answer then 9 mins trying to make sense of the comments,
    I can also do it ‘by moving just one of the matchsticks’

  27. Instantly this time. The clear wording of the question helped.

  28. Eddie says:

    I think the wording ‘…turn this number upside down…’ is ambiguous as it does not say about which axis the rotation should be made. Rotation about an axis normal to the plane of the screen gives a different result to rotation about a horizontal or vertical line on the screen.

  29. Anon says:

    Does “Spoiler + Spoiler” count as a spoiler?

  30. Steve Frushour says:

    Julius caesar would know immediately.

    • Steve Frushour says:

      II = 2 in Latin. Any Roman knows that whether it’s upside down, or right side up, or rotated left or right. SPQR

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