It’s the Friday Puzzle!


Hope you have had a good week.  Imagine arranging 6 glasses in a row and filling three of them with water like this….

Every time you pick up a glass it counts as a move.  What is the smallest number of moves that needs to be made in order to leave the glasses alternating full and empty?

As ever, please do NOT post your answers, but feel free to say if you think you have solved it and how long it took.  Solution on Monday.


138 comments on “It’s the Friday Puzzle!

  1. Jeff says:

    Sadly, a trivial answer. I wonder if my heavy drinking improves or degrades my Friday Puzzle abilities.

  2. 46blyz says:

    10 seconds, but the ease made me wonder if I adn missing something.

  3. ButMadNNW says:

    In about 30 seconds, I have two answers, depending on whether the line has to be Full-Empty-Full-Empty-Full-Empty or can be Empty-Full-Empty-Full-Empty-Full.

  4. Pogo says:

    In fairness there’s only so many decent puzzles to use, at least there’s no ambiguity in the wording, or puppies!

  5. Klaus says:

    15 sec. 1 longer solution, then aha!

  6. Luke says:

    Solved, it drownded on me after twelve seconds…

  7. OutdoorsNerd says:

    I wouldn’t be publishing my time unless it was quick ;0)

    Are you familiar with the Proff’s sneaky ways; it may help? He could ‘take on’ the Real Hustle gang.

  8. vitamentis says:

    There are very few rules and this made it easier.

  9. Terry says:

    Easy peasy lemon squeezy. Solved before I got to the end. Which, as I teach my students, isn’t always the best exam technique.

  10. Spocky says:

    If my solution is right, I got it in under ten seconds.

  11. Tracey says:

    It took me 15 seconds. Assuming my answer is correct 🙂

  12. Superdave says:

    In the spirit of the question and thinking laterally – a small number. Thinking very laterally by using a syphon, no ‘moves’! Is zero a ‘small number’ though?!

  13. Morgan says:

    If I have a bendy straw I can do it in zero! 😉

    Seriously though – v easy this week.

  14. David Rowyn says:

    I think it can be done in 15145 moves.


  15. Philby says:

    Took me less than 10 seconds the first time and about 2 seconds the 2nd time I tried it Might try it a 3rd time but feel my watch hasnt got enough decimal points

  16. @magiademente says:

    A couple of seconds… This puzzle is a classic!

  17. Israel Girón says:

    10 seconds…

  18. Mark says:

    A second or two.

  19. M says:

    Some seconds, but then about a minute wondering if i am missing something.

  20. Toon says:

    about 10 seconds.

  21. Keith says:

    Fairly easy one this week…

  22. marie says:

    a few seconds

  23. marie says:

    If the quiz stays this easy forget it.

  24. Mark Nierada says:


  25. John says:

    3 seconds… but is it a trick question? Can it be done in one move?

  26. Mark says:


    I do hope I’m wrong.

  27. Tom Ruffles says:

    A few seconds, which makes me think I am missing something and will be slapping my forehead come Monday morning.

  28. Timo says:

    i saw the two first sentences and knew the way without knowing the whole puzzle. and read the whole puzzle, instant.

  29. Drew says:

    I am one of the ‘did it in 2 seconds’ group for the first time ever! Hope it is the correct solution :S

    In an unrelated matter, what has happened to the blog on the iPad? Its gone all weird and I couldn’t get to this comments section. Had to get on the pc to post this.

  30. @StratoMagic says:

    Kind of straight away – so quick that I wonder if I missed something…

  31. Peter Boldock says:

    10 seconds to come up with 2 answers (depending whether the alternation begins with a half-full or empty glass (i liked the earlier comment about the glasses not being full!), and then a couple of minutes looking for the trick – now intrigued to ow whether there is one!

  32. Paul Durrant says:

    A couple of seconds only for this classic.

  33. Nichol says:

    one .. I guess there’s none with zero?

  34. @cryopro says:

    1 (326)
    I’m more concerned that it is FRIDAY! When did that creep up on me. That means yesterday was Thursday and tomorrow is Saturday… which seat do I choose??? Front or back… ARRRRRRGGH!

  35. craig says:

    Rather trivial one today, I didn’t pour more than 5 seconds into arriving at the solution.

  36. Simon says:

    I think this must be the easiest Friday puzzle yet – I think it took only a few seconds to solve

  37. Nobby Clark says:

    Alternating “full and empty” has a different answer to alternating “empty and full”.

  38. Dave Rickey says:

    I thought I had it immediately, but while getting ready to post this I came up with a better one (the best possible). So call it two minutes.


  39. FlorayG says:

    easy answer in less than ten seconds. If there’s a harder answer I refer you to Occam’s Razor

  40. Berhard says:

    had the answer instantaneously…

    Then i noticed:

    “Every time you pick up a glass it counts as a move.”… that means if you just pusch the glasses to slide over the talbe the answer would simply be “0”?!?

    (hope i didn’t blabed the “right answer… (if so i’m sorry 🙂 )

  41. @sledgey says:

    It must be easy if I can get it unless …

    Well about 10 seconds

  42. Daniel says:

    Seriously – 2 seconds. This was the easiest puzzle by far.

  43. safc4ever says:

    I got it immediately – I’ve seen it before.

    More interesting puzzle: Replace the water with rum then it’s just 3 moves to end up with empty-empty-empty-empty-empty-[-hic!-]-empty.
    (And me being slightly tipsy!.)

  44. I assume everyone with the “under a minute” solution is wrong 😉
    I got that solution as well, but then came up with a even “lesser” way.

  45. JimC says:

    At first I thought I had misread something, it was so easy, but quickly scanning the comments, it seems that either it really is easy, or many other people have misread it as well.

  46. RaduV says:

    got it really fast ~5 – 10 seconds.

  47. Bletherskite says:

    I got an answer in about 20 secs, seems quite simple so hoping I haven’t been fooled by a devious wiseman twist.

  48. Nick says:

    Thought I had it in 2 seconds then a minute later realised you could do it in even less moves.

    Think it’s a pretty good puzzle

  49. Adrian says:

    0.7834 seconds 😛

  50. Rob says:

    10 seconds for the wrong answer, about 20 more for the right one. So 30 secs in total.

  51. Amanda Thompson says:

    Solved straight away (but I must admit I have seen it before 🙂 )

  52. CH23 says:

    Took me less than a second…

  53. mittfh says:

    Every time *YOU* pick up a glass it counts as a move…

    Does it count as a move if *YOU* don’t pick up the glass…? 🙂

  54. Calum says:

    If I got the right answer, I got it in seconds. However, I created a different problem and solution from the information provided. I imagined the glasses were filled with alcohol; I have lifted three and left the array as empty, empty, empty, empty, empty and empty. Cannot remember what the problem was.

    Maybe someone can do this one in fewer moves?

  55. Todio says:

    Solved before I got to the end. It ~can’t~ be that easy can it? Maybe I’m just getting smarter…

    Or, consider this, the Evil Professor Wiseman (and oh, the possibilities with that name. Wiseman… Wise Man… coincidence? …where was I? Oh, yes) the Evil Professor Watchman slips an easy one in there every once in a while to pump up our confidence “See, honey? I told you I wasn’t a complete idiot like your Mother says. I solved the Whats-his-name puzzle in 5 seconds!” This results in Twittering and Facebooking galore of the puzzle “Hey guyz every1 sez it’s hard but I got it EZ, U should try 2.” thus raising the hit counts in the week following as eager putative egg-heads slavishly anticipate the next Friday puzzle so that they can impress prospective new girlfriends and employers with their mental prowess (always a big turn-on, I hear) Come next Friday though (insert ominous musical sting here) the Fiendish Dr. Wiseguy unleashes an evil puzzle based around a combination of math, linguistics (both domestic and foreign), geometry, lateral logical thinking and the ability to foresee probabilities into another dimension, in colour.

    Well played, sir, but I’m on to your little trick.

  56. Kaspalita says:

    About three seconds.

  57. Kristian says:

    I forgot my stop watch this week, but I reckon I found the correct answer within 1-2 milliseconds (a little slow this week, sadly).

    Silly kidding aside, I found a not-straight-forward-but-not-trivial answer, took me a minute or two after being a bit stuck with a straight-forward solution.
    I hope I didn’t hint too much.
    Good weekend, professor!

  58. Matt Black says:

    Seemed easy to me. Wonder if I’m missing something?

  59. Got it as I was reading the puzzle (so possibly a negative amount of time consumed in the solution process)

  60. pilcrow says:

    About 3 seconds or so. Am I missing something?

  61. Rich says:

    For the first time ever, I actually worked out the answer before I’d finished reading the question. They usually take me ages.

  62. Helen says:

    The glasses are all full – some of them with water, some of them with air…

  63. andreas says:

    Answer after 10 secs, I need 2 moves
    20 seconds later, I realized 1 move is enough

  64. Avner Eisenberg says:

    Two moves. Two seconds.

  65. Veli says:

    Are you allowed to pour in/swap with adjacent glasses only? Am I missing something because the only thing I’m puzzled about is the rules of movement 🙂

  66. Flea says:

    Not so fast ladies, read mittfh’s comment: He’s on the money!

  67. Alistair says:

    Obvious answer straight away. The sneaky way that Richard probably meant, that means 1/2 as many moves, hit me after about 30 seconds.

  68. Alessandro I. says:

    I found 3 solution. The first and second one are the “typical” answer. The 3rd one is a tricky one, and solve the problem in the smallest number of movement. Sure.

  69. niko says:

    Can I use a pump? Joking asside, it’s a fun but easy answer. Took a few seconds to get past the more obvious, and less efficient solution.

  70. Paul says:

    5 seconds. It seems too easy. What am I missing?

  71. NeonNero says:

    Simpler than you think. I’ve actually seen this one before, so it took me about 2 seconds to solve, including reading the question (I saw the illustration and already started picturing it before I read the text).

  72. Psikita says:

    Easy one, I think … 🙂

  73. It took me about a minute. Good puzzle – I like it when I’m forced to think laterally when solving a problem.

  74. Magic Iain says:

    Got it in 10 seconds or so. Never done one of these before though so might be wrong!

  75. Coquejj says:

    Quite well known, I think. A good puzzle for those who didn’t know it before.

  76. Joao Pedro Afonso says:

    Ok, I got it, two ways, 30 seconds

  77. Gerard Engelage says:

    About 20 seconds to get to my second and final solution. I’m still assuming it is THE solution that will come up after the weekend.

  78. JJ says:

    About a second to get the answer. Nice little puzzle, though.

  79. Adrian says:

    You’ll need 14 shirts. Damn it, am I too late again?

  80. Antonio says:

    Two seconds. Four, in fact, but just to be sure.

  81. Kirk says:

    Easy one. Thought I had the answer before I finished reading the question… then realized there was a better one. cute puzzle.

  82. Sari1967 says:

    Maybe I am cheating but got it straght away before I had finished reading the puzzle

  83. is it allowed to poor the water in an other cup?
    then i saw it in 2 seconds.

  84. Rosie says:

    I think I’ve got it but… I could be wrong ;D

  85. NoAstronomer says:

    Took me a little less than a minute. I had an obvious number within a few seconds, then I wondered if I could reduce it. Thinking about the wording of the puzzle and what it did *not* say lead me to the answer.


  86. Jerry says:

    Can glasses be switched? Or must you leave the glasses in place and only pour the liquid from one glass to another?

  87. feliks says:

    Richard and his lateral thinking. 😛

  88. GuyK says:

    Oh, there is a less than zero moves solution :
    you’ll have to travel time backward .
    (hint : ^Z^Z^Z^Z)

  89. Zach says:

    5 seconds

  90. Gus Snarp says:

    I assume I’ve got it, but it can’t possibly be this easy, so I must be wrong.

  91. majikthijs says:

    I suppose cut and paste is not an option? In that case zero moves with a bendy straw, one move without.

  92. Michael5MacKay says:

    Less than 30 seconds. Next time I’ll use a stopwatch so I can be more accurate. Now I think I’ll see if I can download Paranormality on my kindle.

  93. Noel says:

    Are the glasses up against eachother or is there space between then ? This would change the answer

  94. […] It’s the Friday Puzzle! Hope you have had a good week.  Imagine arranging 6 glasses in a row and filling three of them with water like […] […]

  95. Mr. D says:

    I’ve seen this one before, so I got it instantly.

  96. katie k says:

    I got an answer right away, but it seems to easy. In fact, I have two answers depending on the interpretation of the question.

  97. Daryl says:

    it took me 2 seconds. the picture alone put the concept in my head, i just had to finish reading the question and test it in my mind to find the answer

  98. Sarah says:

    I got it immediately, seems pretty obvious

  99. Billy says:

    <4 seconds 1st try 😛
    haha easy this week

  100. rodney says:

    this was way to easy, i got it without even reading the question i knew exactly what it was

  101. Cosmin Romania says:

    I got this one quickly 😀

  102. Jules says:

    Like several others, I got the answer between seeing the illustration and getting to the end of the description. Maybe 2 seconds.

    I then spent five minutes reading through the comments and despairing at the participants who for some reason are unable to show consideration for others by posting their answers.

  103. Noel says:

    My wife worked it out almost instantly.
    I see what I missed now

  104. D says:

    Isn’t the solution easy? I knew what to do isntantly.

  105. Seth says:

    2 Solutions. instantly after reading.

  106. Berber Anna says:

    Instantly, but it seems too easy. Maybe I misunderstood something.

  107. The Prof says:

    2 seconds

  108. Marion says:

    Recoginsed the picture before reading the puzzle so already had the answer when I finished reading.
    Just joining in with the general paranoia now in thinking Richard has tricked me and it isn’t that simple!!!

  109. Luckily about ten seconds………any longer and I would have moved on!

  110. Cheree says:

    My dream retirement would probably be a few decades in various countries, enjoy and absorbing the world around me with a loved a single!

  111. write essay says:

    This can be the worst post of all, I’ve read

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