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.


  1. 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.

    1. just go around the talbe and watch the row from the other side, or count form right to left… (So i seen no differece between Full-Empty-Full-Empty-Full-Empty or Empty-Full-Empty-Full-Empty-Full)

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

  3. 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.

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

  5. 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?!

    1. Same smart zero move solution,
      but with a straight straw and a large capacity cheeks tank
      or an extra bottle of this shiny blue water.
      But if the water is this kind of blue, I wouldn’t drink it.

  6. 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

    1. Sigh (again).

      Which part of “as ever, please do NOT post your answers” did you not get?

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

  8. 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.

  9. 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!

  10. 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!

  11. 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.


  12. 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 🙂 )

  13. 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!.)

  14. 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.

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

  16. 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

  17. 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…? 🙂

  18. 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?

  19. 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.

  20. 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!

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

  22. 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 🙂

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

  24. 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.

  25. 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.

  26. 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).

  27. 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.

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

  29. 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.


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

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

  32. 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.

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

  34. 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

  35. 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.

  36. 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!!!

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