It’s the Friday Puzzle!


The Essential Magic Conference has now uploaded all of the videos from all of the sessions, and you can watch them for just $75.  It’s a bargain, go for it!  OK, to the puzzle…..

Yesterday I saw a drinks machine that had three selections – Tea, Coffee or Random (Tea or Coffee).  However, the machine was wired up wrongly so that each button does not give what it claims. If each drink costs 50p, what is the minimum that you have to put into the machine to work out which button gives which selection?

As ever, please do NOT post your answers, but do say whether you have solved it and how long it took.

See you Monday!


87 comments on “It’s the Friday Puzzle!

  1. Travis says:

    As worded, the solution took me only a moment to work out. I think the question may be misworded.

  2. Pradyut says:

    Took only a few moments to figure it out

  3. Roland says:

    Solved it in 10 seconds

  4. Warren says:

    I think the question may be misworded too, but either way it’s an easy one.

    • Warren says:

      …then again worded the other way (maximum vs. minimum) it’s the same answer!

    • Tommy says:

      I don’t see how maximum could be the same unless the “random” button is just alternating between coffee and tea rather than truly random.

    • Warren says:

      I think you’re right Tommy, it would take at least one additional press?

    • M says:

      The puzzle is worded correctly. And the random button is just alternating between coffee and tea, that is what it says. The word “minimum” is correct. You can always put more money in it, but it should not be neccesary if you do it the right way.

      We have had a puzzle like this one before. So it was very easy.

  5. Pete says:

    Took me a minute (it’s late/early), but I got there.

  6. Rob says:

    Done while reading. It’s another guise of the old apples and oranges puzzle.

  7. fluffy says:

    Yeah, just a slight rehash of the apple and orange one from a couple months ago. Yawn.

  8. Navneeth says:

    This has been done before but with a different form of food.

  9. Lemur says:

    Why would it have a random button?

    It took me ’til the end of the question for the reasons stated above.

  10. Michael Kingsford Gray says:

    I think that I have worked-out the correct answer. I spent 20 seconds arriving at it, and a further 60+ seconds to determine if it could be as simple as it seems to be!
    I’ll see on Tuesday. (We are all time-lords in Australia)

  11. sam packman-fullbrook says:

    wooo hoo. i can actually do this one! i know dead easy but it made me feel smart achieving one 😀

  12. Rusty says:

    Yep. Got it. And, as I HATE coffee, I also know the maximum I would need to put in to be sure of getting a cup of tea.

  13. Stephen J Hensrtidge says:

    About a minute

  14. J.H Theart says:

    This is way to easy

  15. lilabyrd says:

    Maybe… just maybe make me feel better after last week’s but really way too easy if I did this right ….. just until the end of reading the question and a minute to work it out….humm….yep I feel good……. :}

    • Joao Pedro Afonso says:

      Lila, didn’t we solve a problem like this not so long ago, here?

    • lilabyrd says:

      Joao Pedro, sort of ….. I think we had oranges and apples? And one mixed and we needed to fix the labels that were all wrong and we could only look inside one box to set them right?……apple & oranges…….coffee & tea…..hmmmm…..

  16. J Kane says:

    Oh I’m too tired this week to hunt for my lost brain… I could have worked this out at primary school in a second. Suddenly I am old and redundant.

  17. Solved it in a minute. I like this one. 🙂

  18. Katharine says:

    It took me two minutes to realise my 1st answer, arrived at in 2 seconds, was wrong then another 2 minutes to get the ‘right’ answer

  19. Lindamp says:

    2 or 3 minutes, as I initially started off on the wrong track. If it *is* a rehash then I’ve forgotten the older one so it made me feel good to work it out!

  20. Mark Grady says:

    Less than a minute to get the answer and check it through. Had to check as the wording of the question is right but could be misinterpreted.

    This isn’t one of the best Friday Puzzles there’s ever been.

  21. Joao Pedro Afonso says:

    Nice, Back to the easy puzzles. About half minute.

  22. Kirsty Jolly says:

    Thank you. Solved in a flash. This made me feel clever 🙂

  23. Berber Anna says:

    Got it. Had to do some extra thinking to get to the best solution, but it was still a fairly easy puzzle.

  24. Bernhard says:

    The time to read it (I just knew the riddle).. 🙂

  25. Stephen Barnes says:

    About 5 seconds, provided I understood the question.

  26. Bletherskite says:

    I figured it was a rehashing of the old apples and oranges puzzle but took me a couple of minutes to just reveiew it and come up with my answer.

  27. Richie says:

    About 10 seconds.

  28. D says:

    Easy, 10 seconds. 😀

  29. Reggie says:

    Thought i had in 5 secs, but reviewing got me the correct answer a minute later. 🙂

  30. Simon H says:

    It took me about half an hour, but only thirty seconds of that was after reading the question properly and spotting the key info (the bit that Beranger points out). D’oh.

  31. Simon H says:

    p.s. if the question isn’t worded wrongly, then it’s worded clumsily. I think we’re presumably looking for the smallest maximum amount that you’d have to spend in order to be 100% sure in all cases.

  32. Mark says:

    Ah yes very simple. The case is far more interesting if the buttons aren’t labeled at all… 🙂

  33. carlos says:

    nice one, few seconds.
    This seems a good puzzle for non-puzzlers.

  34. Joao Pedro Afonso says:

    Beranger, considering that you must have read all the puzzle text, did you read the part where it says: “As ever, please do NOT post your answers,”?

  35. lilabyrd says:

    Now, now Joao Pedro you know that doesn’t apply to EVERYBODY……oh hmm no sorry I’m wrong….THAT DOES APPLY TO EVERYBODY…..was that what you were thinking too?

    • Joao Pedro Afonso says:

      I think our replies became orphans :-p

      This is instructive but weird at the same time: who will guess what happened? Our comments here now doesn’t appear to make any sense. Answers to questions forgotten… maybe many of the weird comments and historical mysteries I see sometimes are reactions to disappeared pieces, wise guys becoming loonies.

    • lilabyrd says:

      oops! Joao Pedro me thinks Richard took down the post that gave the answer…..looking back my post looks mean…..I meant it to be funny sort of a poke as not to give the answer away…..sorry if offended anyone… :{ ….. I will be better….. :} …..

  36. Corrine says:

    Think I solved it, very quickly!

  37. […] Wiseman has a nice retelling of the apples-and-oranges puzzle (which incidentally was a regular interview question at a company I used to work for): Yesterday I […]

  38. Sidebernie says:

    2 seconds to get a gut answer, and then another minute to convince myself that it was right.

  39. Ken B says:

    Is this any different than the Apples/Oranges/Both question a few weeks ago?

    • rmb says:

      To me also it looks the same puzzle, just worded differently, about wrongly labelled boxes of ‘apples and oranges’ published on March 26, 2010.

    • Berber Anna says:

      For me, due to the different wording, this one was much easier to imagine. That made solving it much easier (I didn’t even start on the other one, while this one only took me a few minutes).

  40. Thirty seconds – as long as the answer begins with same letter as the capital of Sierra Leone

  41. arensb says:

    It took me about 20 seconds to figure out the key insight, and a further three minutes or so to work the details out on paper to my satisfaction.

  42. Navin says:

    2 min

  43. Tuiã says:

    Less than 1 minute. This problem works pretty like a scientific model. Am I right?

  44. Jerry says:

    Solved it in a minute or so. Very similar to a past puzzle. Write out the possibilities and see which ones you can eliminate and why.

  45. I think that i got it… 😀

  46. jbabb says:

    I thought I had the right answer a few times, but after rereading the puzzle twice (apparently, I skimmed the wording and missed a few details each time), I’ve solved it in ten minutes.

  47. JeeMiNee says:

    I did not know this puzzle. I found it too difficult to solve by myself. Reading all these remarks about apples and ornages made me google ‘oranges apples random puzzle’ so I read the solution elsewhere.

  48. slightly_skeptical says:

    Good one, 5 minutes. Read the question carefully.

  49. […] It’s the Friday Puzzle! The Essential Magic Conference has now uploaded all of the videos from all of the sessions, and you can watch them for […] […]

  50. christine says:

    Love it, at first I thought it was something that it turned out not to be .. then after 3 minutes I had an “ahh Ha” moment and got it a minute later.

    …or so I think … good one Thanks

  51. Marcus Stefan Brodeur says:

    Solved it in about fifteen seconds.

    It’s similar in many ways to that old puzzler where linked classes of content are printed on opposite sides of a certain number of cards, and the question is how many cards you need to flip over to prove/disprove the ostensible rule.

  52. Hole says:

    Fantastic A-ha moment!

  53. G-man says:

    confused at first thinking a random button could produce tea endlessly therefore would be indistinguishable from tea button. Then I read the question again.

  54. Ole Jacob says:

    First: Me like tea.
    Second: this one was easy…

  55. Bethany says:

    2 seconds, I thought too many in the first second, and brought it down to the right number in the next second.

  56. katie says:

    I started writing it out, but then it just came to me. I’m pretty confident I got the right answer. These are my favorite kinds of puzzles. Feel free to post as many of them as you like, Richard. 🙂

  57. DaveL says:

    10s after re-reading the question /exactly/

  58. BigBadEd says:

    it took a couple of minutes to convince myself of my answer and now I satisfied

  59. BigBadEd says:

    what puzzles me most is the order in which the comments are post if the timestamps are correct…

  60. Enrique says:

    10 sec for the A-Ha!
    3 min to expain it in words

  61. 10 sec for the ‘A-Ha! moment’
    3 min to expain it in words

  62. Paul Durrant says:

    I spent half a minute thinking I knew the answer, and that it seemed a bit strange. And then I re-read the question and noticed the vital bit, after which the answer was clear, and not so strange.

  63. namowal says:

    It took about a minute to figure the minimum price, but I had to draw a picture first.

  64. Joao Pedro Afonso says:

    To give to understand we know the answer without playing the answer, is an art and a game. I expect to see Beranger next time, more subtle.

  65. George says:

    finally one my brain can capture. one minute

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    what is the answer

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