It’s the Friday Puzzle!


You are trapped in a prison and the guard decides to play a game.  If you win, you will be allowed to leave.  But if you lose, you die.   The guard says that he is thinking of number 1, number 2, or number 3.  You are allowed to ask one question to find out which of these three numbers the guard has in mind. However, the guard will only answer with a “yes”, “no”, or “I don’t know”.  What should you say to the guard?

As ever, please feel free to say if you think you have a solution and how long it took, but please do NOT post your answers.  Solution on Monday.  Have a good weekend!


95 comments on “It’s the Friday Puzzle!

  1. lilabyrd says:

    What did we do to you that you keep wanting to kill us?

    • Anonymous says:

      Richard’s not a psychologist but a psychopath. The beginning is the same, but the end is very different! 😉

    • lilabyrd says:

      lol …. how very true!
      I’ve thought of several things….one being “please, please, please don’t kill me!”… lol… I’m sure that isn’t the answer.

  2. Christopher says:

    About five minutes this time.

  3. Malinari says:

    I think the fact that guard seems to have a “God” complex by so nonchalantly wielding the power of life and death, and therefore his answer to my question is likely to be untrue (what am I thinking, no wrong, death it is then….). I’ll lead the other prisoners in open revolt and play better odds of survival, thankyou 🙂

  4. beanfeast says:

    I think I have an answer. I’m not too happy with it though because it seems to make an assumption about the level of education that a prison guard has.

  5. Nick Sharratt says:

    A couple of minutes to think of 2 “answers”, neither of which feel likely to be the ‘right’ ones -one maths based and one logic based.

  6. Mark says:

    Mmm well I have an answer but is it the right one?

  7. Brian G says:

    I have one, but I doubt it’s the right question.

  8. Mike Torr says:

    I did this while driving to work, so road traffic distracted me, but I managed to get an answer in ten minutes. I think there’s clearly infinite different answers to this, but the idea is presumably to determine the required general strategy, which I think I have.

    I agree there is a small assumption here that the guard is numerate and doesn’t lie 🙂

  9. Faye says:

    Oooh i dont like this one!

  10. daveman says:

    I knew this one already, btw u assume the guard answers truthfully to ur question.

  11. Graham says:

    I got an answer within two minutes. I get the feeling it won’t be the one that’s posted.

  12. Patrick says:

    Easy. Though my solution is probably not official and slightly rude to prison guards.

  13. writerJames says:

    Hmm, got one that seems rather neat in about a minute… Will be interested to see what other ways there might be of doing it.

  14. Johanne says:

    Got it, but it only works on the condition that the guard anwer truthfully.

    About two minutes…

  15. About one minute. Of course it depends on the guard’s honesty – but that’s part of the ground rules for this sort of game, isn’t it?

  16. Colin Coghill says:

    Phew, that was tricky. Saw the shape the answer had to be straight away but took about 10 minutes to work it out. 🙂

  17. jh says:

    I got a solution in two minutes and later on two more variations based on the same idea.

  18. Anonymous says:

    Can someone do me a favor and email me the answer? I’m buggin’ out over here.

  19. noam says:

    Ask a silly question, get a silly answer. I got a silly answer before I finished reading the question.

  20. D says:

    I have one that works, but will almost certainly not be the official answer. 😛 It requires the guard to be honest and also have a good knowledge in genetics.

  21. lordmanley says:

    I have an answer, but I think it might well be wrong.

    I assumed that the guard would be honest in his response and that I am not allowed anything as simple as:

    “say ‘yes’ if you are thinking of 1, say ‘no’ if you are thinking of 2 and say ‘don’t know’ if you are thinking of 3” 😉

  22. jane kelly lil miss and whtever says:

    Hmmmmmm why should he say “I dont know”……..
    Im still trying to find the answer….

  23. jane kelly lil miss and whtever says:

    oooooo i got it!!!!!
    i think!!!!! is it a trick question???

  24. Paul C. Anagnostopoulos says:

    I think I have a solution. It took me about three minutes.

  25. jon says:

    solution immediately.

  26. Timothy says:

    “The guard says that he is thinking of number 1, number 2, or number 3. ”

    I don’t get that formulation … so, is it ANY three numbers (in a sense of: he is thinking of numbers A,B, and C) or is he thinking of THE numbers 1,2, or 3?

    confuses me! 😀

  27. elsiem says:

    I’m still working on an answer, or rather a question (10 minutes so far) but am moved to comment on that photograph of the guard, which is simply marvellous.

    • lilabyrd says:

      Yeah but is that part of a trick? Cause based on one of our more recent surveys he may only be of use as eye candy…lol…..

  28. Gus Snarp says:

    I haven’t got an answer yet, but what’s with that guard picture? Is this prison porn? I think if I were gay I might just stay in the cell with him.

  29. Dennis says:

    I have a math-ish question that took me about 5 minutes to come up with. Seems unlikely but I think it works…

  30. David Wiley says:

    I think your prison guard’s pants are held together with Velcro.

  31. Rob says:

    5 minutes of sustained headscratching to arrive at watertight answer. No cheating or Googling this time. Nice puzzle.

  32. Rob says:

    BTW how is the guard in bed? LOL

  33. Ken T. says:

    I guess I would have to ask, “Is that a regulation hair cut? Because it looks a little shaggy to me.”

  34. Sylv666 says:

    I’d like it on record that I’d be more than happy to be held prisoner by that guard

  35. Berber Anna says:

    After thinking a while, I did come up with an answer that would probably work the way I want it to work, but it’s phrased in a fairly ugly way…

  36. Matth35 says:

    Got this in five minutes. Not sure it’s right but it seems to work when tested.

  37. Ken B says:

    Can we assume that the guard must answer truthfully? It’s not explicitly stated, and I can’t think of a way to solve it if he’s allowed to lie.

  38. Cuneiform says:

    Of the recent puzzles, this was the easiest for me – took me a minute or so with the initial hunch of what to ask a few seconds after reading. There are many variants to my solution.

  39. Vee says:

    Umm, that guard looks like a stripogram… but I have one question and it took me about 5 seconds to think of it.

  40. Jayson says:

    Got an answer in about 2 minutes, prob not correct. We’ll see

  41. Nikodemus says:

    Under a minute for the core idea. Crafting a question that actually implements the idea somewhat longer.

  42. João Pedro Afonso says:

    I think there are several ways of doing this, although, maybe not very elegant any of them.

    Nice puzzle…

  43. Dan says:

    I have an answer (or question rather) and unlike a lot of other people posting I feel pretty confident about it…..*smugness*

  44. This is a bad puzzle (only the second bad one that I can recall). There is a direct mapping of 3 number/answer pairs, so the only thing to do is make up a suitable question. The computer scientist in me got *a* solution immediately, but there are an infinite number of questions that would serve as solutions. Maybe a better puzzle would be how *short* a question can you think of that saves your life?

  45. Mark S says:

    I’ve got one, took about 2 minutes.

  46. Rachel says:

    Got it! About two minutes. I’m getting better at these.

  47. Ben Hastings says:

    I have an answer that I believe provides the solution. Took about a minute. Of course, it’s maths/logic related because that’s my area of training.

  48. bananacat says:

    Can someone please give me a hint? I’m having some brain fog today.

  49. Mervulon says:

    I don’t recall a prison guard amongst the cast of the Village People, but that was a long time ago…

  50. Ken B says:

    It’s a silly question. Everyone knows the three choices are “Yes”, “No”, and “FileNotFound”:

  51. Jamal Wills says:

    By Jove, I think I’ve got it! In just a couple of minutes or so. I’ve got to start timing myself. I’m usually pretty horrid with games like these but I’ve answered a couple pretty easily.

  52. erica says:

    Got it in about 10 minutes.

    The breakthrough was realising I needed to utilise all three possible responses.

  53. […] It’s the Friday Puzzle! You are trapped in a prison and the guard decides to play a game.  If you win, you will be allowed to leave.  But if […] […]

  54. gamegeneral says:

    I have an idea of what a good question might be, but if the guard’s mathematically challenged, it might be hard…

    I’d probably have to phrase it carefully so that even the guard would understand. It’s a given that he can’t lie, right?

  55. DrGreen says:

    4-5 minutes to one solution. This is harder than the others. Thanks for it!

  56. B says:

    goog one Richypitchy. kept me busy for a few minutes!

  57. Flavio says:

    I got an answer in about 5 minutes.

  58. Emma Dunlop says:

    Had a little think, is the answer perhaps:

    ‘Is the number you’re thinking of less than 2?’

    A ‘yes’ answer would mean it had to be 1, ‘no’ would mean 3, ‘don’t know’ would be 2 perhaps? Just a guess!!

    Emma x

    • B says:

      You didn’t read well!

    • B says:

      you mist the last paragraph I will copy it for you.

      …As ever, please feel free to say if you think you have a solution and how long it took, but please do NOT post your answers….

  59. Emma Dunlop says:

    In fact, no that wouldn’t work! Scrap that last post lol!

  60. ScreamingGreenConure says:

    Guess what? Some of us have created a TEAM ANSWER. We laughed, we cried, we got distracted by cartoons and butterflies – but in the end, we did it. If it’s not right, our new friendship will be shattered and we will be broken individuals.

    • ScreamingGreenConure says:

      Okay, my buddies want you to know that the butteflies are all in my bedroom (in pupae form) so did not distract them, just me, and the cartoons were inside my head, and so it was just me distracted by those too.

    • DG says:

      We were distracted by ScreamingGreenConure’s distraction.

    • Berber Anna says:

      She distracted us from distracting her. Be glad, we still wouldn’t have solved it if she hadn’t. Thank you, butterfly pupae. We owe you our freedom.

    • ScreamingGreenConure says:

      I’m very distracting. Look, I’m distracting you right now!

    • lilabyrd says:

      Well SGC lives…I was wondering if you got lost in the future trying to find the answer…lol…with all the distracting going on did anyone get distracted by the guard? Remember your life is in his hands….lol….hmmm….now that’s a thought…… ;}

  61. SavvY says:

    Hm. . That was easy i guess. . Less than 1 min. . . . But my answer may be wrong. . Let’s see

  62. Michael Kingsford Gray says:

    Hah, after a few minutes wondering if the problem *might* be related to the famous “Monty Hall” problem, I abandoned that path and asked the guard a tricky question…
    (I assume that the goal to seek is to not get killed?)

  63. katie says:

    Oh wow, I have run through everything I can think of and none of them are passing the test. I don’t know. Infuriating!

  64. Suzanne says:

    I think my question is “Does the ‘Prisoners’ Last Meal’ menu have a veggie option please?”

  65. Cosmin Romania says:

    The guard is actually thinking?! Well, that’s something new.
    I might have an answer, but it probably isn’t the right one.

  66. Leah Doughty says:

    10 seconds. Still a good puzzle

  67. Alyzabeth says:

    If you added the number you are thinking of to three, what would it equal?

  68. Alyzabeth says:

    Whoops, sorry, how do I delete my post? I didn’t notice the “don’t post your answer here” at the top. My bad!

  69. Osama says:

    The question would be,
    Is the difference between your number and the number 1 an even number?
    If he said yes, then the number is 3 (3-1=2) even
    If he said no, then the number is 2 (2-1=1) odd
    If he said I dunno, then the number is 1(1-1=0) neither even or odd (dunno)

    This answer can’t be proved wrong 😛 I hope 😛

  70. Anonymous says:

    zero is even.

    • Anonymous says:

      Oh yea!! But may be the guard is bad in math, and he would say “I dunno” :p
      btw, where should I post my answers, if not here?

  71. SteveG says:

    “When you divide the number you’re thinking of by that number -1 (x/x-1), is the answer greater than 1.75?”

    3 – If the number is 3, the expression is 3/ (3-1) = 3/2 = 1.5 – answer ‘No’ (NOT greater than 1.75)
    2 – If the number is 2, the expression is 2/(2-1) = 2/1 = 2 – answer “Yes” (greater than 1.75)
    1 – If the number is 1, the expression is 1/(1-1) = 1/0 = undefined – answer “I don’t know”

  72. Jamal Wills says:

    How about this:

    “If I guess incorrectly, would your number be larger than mine?”

    If “yes” then hypothetical guess {1,2} => 3
    If “I don’t know” then hypothetical guess {1,3} => 2
    If “no” then hypothetical guess {2,3} => 1

  73. Alka says:

    Want to subscribe for Frday puzzle.

  74. foo bar says:

    foo bar

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