It’s the Friday puzzle!


OK, I really will get around to looking at the lies over the weekend. Keep them coming. So, to the puzzle….

Can you take the clock face below, and cut it into four pieces such that the numerals on each part add up to the same number?

clock1So, for example, this solution would not work because the numbers on the four pieces add up to different amounts….

clock2The answer to this puzzle, and 100 others,  can be found in a new kindle ebook called PUZZLED, and is available in the UK here and USA here.

110 comments on “It’s the Friday puzzle!

  1. zoethaeque says:

    Wow! Just bump on this wonderful blog. Hm, 5-10 minutes I think? To solve this puzzle I mean.

  2. fluffy says:

    After about 30 seconds I know what the twist has to be but I haven’t thought it through enough to figure out how to apply it.

  3. fluffy says:

    Oh and then it only took a couple more minutes. Cute.

  4. Stefan says:

    Hah! Solved it. 5 minutes.

  5. About 5 mins. No clues – let ’em suffer🙂

  6. Nick Sharratt says:

    About 3 minutes and I have an answer that works and is based on what I’m sure the trick is, so pretty sure it’s the ‘right’ answer too. Spotted what I believe the trick is in about 10 seconds, but then took a while to find how to make it work.

  7. Martijn says:

    Tricky, but I found a solution in 10 minutes

  8. Smylers says:

    I can think of two possible tricks, but initial playing around with numbers hasn’t got me anywhere with either of them — will try again later.

    • Smylers says:

      Had time to look at it properly now — added up the numbers 1 to 12, made a guess as to what the total for each piece would be, then saw a solution straight away (using both tricks).

  9. Egon Elbre says:

    30 seconds…
    This reminded me of a story about Gauss’s schooldays (can’t say what the story was because of the clues in there).

  10. Minnie says:

    solved in 10 minutes

  11. Sallybm says:

    2 minutes or adding up, easy squeezy!

  12. […] can vote on the original post if you need a […]

  13. Jenny says:

    Done in a few mins, but do you mean the individual numerals or the numerals *as grouped*? I did the former (think it has to be?). And if the twist is what it has to be (if it’s the former) then maybe the wording of the question could have been a little bit more careful.

  14. Neil2Russell says:

    Within a couple of mins. Like the pattern – looks elegant.

  15. mandydax says:

    I really liked this one. Did get the solution in about oh “:59 Seconds”! Hehe, it was a good thinking puzzle.

  16. Timo says:

    solved in two minutes

  17. Theophrastus says:

    Well I worked it out yesterday before I’d even seen it.

  18. Z says:

    A few minutes, a good warmup before facing “real” problems at work ^^

  19. Marcin Wrz says:

    nice. solved in about 5 minutes.

  20. Daan says:

    Did everybody notice it has to be divided into FOUR parts?

    • Yes – definitely doable but I suspect I know why you said that. Clue: [Hidden]

    • Daan says:

      Indeed doable. I solved it first in 30 seconds, but then it was not divided into 4 parts (later on I read the comments and that one clue someone posted, which was why I posted about the four parts😉. Trying to divide it in four parts was harder, but still possible.

  21. Dan says:

    I got it! Woo hoo! About 30 secs.

  22. Geraldine says:

    I suspect I know what the trick to it is, but I haven’t had my morning coffee yet so can’t get my brain to summon the energy to work it out properly!

  23. Bugs Man says:

    Got the answer eventually – the principle was immediately obvious, but implementing it correctly took me an age!

    Afterwards I did a Google and found at least 3 alternative solutions, but all based on the same principle.

  24. lakritze says:

    I’ve got a solution, but it’s rather a hair-rising one. Spent about eight minuts on that.

  25. theophrastus says:

    I don’t have the answer – it’s shocking, I know, that I lied above – hey I should put that in the lies thread – but I think I know what the trick is. I’m assuming that to make this work, the clock face has to have Roman numerals, not arabic ones?

  26. Will says:

    I think I see the twist in the puzzle.

  27. Finally one that I worked out and fairly quickly too (in less than 5 minutes)

    God bless my mathematical parents and their obsession with numbers!

  28. unrivalled says:

    Got it – for sure!

    Took under 30 secs to get the trick, and under 5 mins to actually work it out – had to use a piece of paper though (Similar to Geraldine, the morning coffee hadn’t kicked in!)

    Liked this one – one of the better puzzles.


  29. John says:

    Like most worked out the strategy fairly quickly then took a few more minutes to work out the solution

  30. Craig says:

    Cheeky twist, took about 4 minutes

  31. Steve says:

    Took a minute or two though, admittedly, I think I’d seen a similar puzzle before.

  32. Jarak says:

    Done with out reading the replies or getting the hint in under 1 min.

  33. Got it! ~5 mins (easy once I figured out the magic number).

  34. Justin says:

    I’m pretty sure I got the same solution as Neil2Russell. It took under a minute to figure out the trick, then I used the Gimp to draw the lines. It took a couple of tries to work out the solution.

  35. DeepField says:

    Done. About 5 min.

  36. Garrett says:

    Simple enough. Did the quick calculation to find a straight forward approach was impossible. The trick was pretty obvious from there.

    Came up with the first solution in a couple minutes, then 3 other solutions quickly after.

    I can only think of 4 possible solutions, anyone come up with more than that?

  37. Sidebernie says:

    There’s already a sort of subtle hint in the picture itself. I don’t think an additional hint is required. Like a lot of others here I got the twist right away, and took 4 or 5 minutes to make it work out correctly.

  38. Robert says:

    Yeah, pretty certain I got it. I figured out the trick once I realised 12! is 78 and then took a few minutes just to see how exactly how to cut it.

  39. killyosaur says:

    I must be the idiot of the group because I am still not seeing it.

  40. Egyud says:

    Got it. Now I can get on with my morning. Thanks that was fun.

  41. Steve says:

    @killyosaur: It’s very simple. 1+2+3+4+5+6+7+8+9+10+11+12 = 78, so all you need to do is divide up the numbers into groups of 19.5. 🙂

  42. Engywuck says:

    @Robert: 12! isn’t 78 but we know, what you want to say😉
    Like Egon it reminds me immediately of gauss’ schooldays.
    Took me about 10 minutes to find a simple solution.
    @Tortorific: It works even with correct roman numerals!

    Nice puzzle!
    Like Neil2Russell I’d say it looks elegant🙂

    @Garrett: There are for sure 5 or even more possible solutions, if you are trying really hard😉

    • lakritze says:

      Correct Roman numerals? Then I’m really looking forward to your solution.

    • Garrett says:

      Got up to 8 solutions by interpreting the rules loosely. I’m sure there are plenty more, but not in the mood to keep searching.

      I’ll post pictures on Monday if someone doesn’t beat me to it.

  43. slightly skeptical says:

    5 minutes, the tricky part was expressing decimals in roman numerals.🙂

    • killyosaur says:

      That seems to be the issue I’m having, and can’t seem to figure out. I’ve spent too much time on this already though, back to the ol’ grindstone.

  44. robert says:

    after doing the math and realising it wasn’t that easy but once i knew that took about 1 minute with an overhead projector pen and my computer screen but will admit i never scrolled down to see the example, so i pleased with myself.

  45. NYD says:

    Ahh, there’s a dead givaway. Mr. Wiseman, you had me going for about …well I really don’t know. Time is quite relative when your not wearing a watch.

    P.S. I really like 59 seconds. for the most part it makes quite a lot of common sense. I reckon it will make even more sense the second time I read it.

  46. Steven Harris says:

    Time is only relative if Big Ben is your uncle.

  47. About 5 minutes in total. 10 seconds to calculate it was impossible. Another 20-30 to figure out the trick to the trick. The rest of the time was playing slice-and-dice in a graphics program. I’m looking forward to seeing if there are cleaner cuts than what I came up with.

  48. AUTOPHASE says:

    great brain teaser, just passed about 12 minutes of work time.

  49. I LIKE this puzzle!

    I feel I would have solved it faster if it wasn’t so late at night. There were some “I should have realised that earlier” moments.

    As it was, it was just the right level of difficulty to keep me motivated until I solved it.

  50. nannes says:

    @AUTOPHASE Glad I’m not the only one who needed more than 5 minutes!
    Took me 12 too. Saw the trick directly, but it took me some time to find the right pieces. Although I guess there are more solutions than 1.

  51. zz says:

    (1+2+..+12 )%4 != 0

  52. Raymond says:

    Also took me about 5 minutes. Can you solve the it for a normal clockface like this one : ?

  53. dani says:

    once i figured out the joke… it didn’t take that long… heh, heh, heh…

  54. Graham says:

    I was involved without looking at my watch – but 5-10 minutes I think> A good one.

  55. Oase says:

    Om IX uur had ik het ineens…

  56. Anonymous says:

    less then 2 min.

  57. […] Google Reader: It’s the Friday puzzle!, DINOSAURIOS DE […]

  58. Alan says:

    Enjoyed this one. 5 mins or so.

  59. namowal says:

    Fought with this all morning durring occasional spare moments, than sat down to work on it “for real” and solved it in a few minutes.
    If the solution’s what I THINK it is (didn’t check the comments because I was afraid of spoilers), there’s a slight twist…

  60. Gordon says:

    Hmm… took maybe 2 minutes. I’d feel more comfortable of my answer if 9 was written as VIIII.

  61. Gordon says:

    Strike that… VIIII would be worse.

  62. B4sti4n says:

    2 or 3 minutes. i think there is more than one possible solution, but one is enough for me…

  63. Sanel says:

    I didnt get it, realy, am i the only one? i checked the answer (page source) and sudenly i understood how stupid i had been, but after that i found two more possible solutions! but it should be possible to find more i believe!

  64. Eddie Fritz says:

    Have spend almost 5 and 1/2 hours on this puzzle. I’ve considered every possibility and I am confident when I am saying that the answer is that it’s not possible. I think you guys should recheck your answers because I know for a fact it can’t be done.

    • Read the question VERY CAREFULLY (and understand each word). It can be done, I promise you.

    • You are imposing rules that weren’t given in the problem. You’ll be kicking yourself when you see how easy it is.

      Took me about a minute to realize it couldn’t be done with the constraints you naturally want to impose and the solution became obvious. Took another couple minutes to work out the exact cuts in photoshop. No improperly formed numerals necessary… none.

  65. […] It's the Friday puzzle! « Richard Wiseman's Blog […]

  66. woupiestek says:

    The first thing I wanted to know was what number would go in every part. So I added all the numbers, and found out I needed a trick. Once I found the trick I was satisfied, and didn’t bother to finish the puzzle.

  67. Steven Harris says:

    Came back for another go.

  68. shpalman says:

    Ok, now I know the total on each piece (and the trick) it’s easy. Of course, working out the total of 1+2+3+4+5+6+7+8+9+10+11+12 and dividing by four suggests it’s impossible (while three or six pieces is trivial) but Roman numerals work in a different way…

  69. Shona says:

    I think I know how it’s done, but I’m crappy at roman numerals at the best of times and I’ve just woken up.🙂

  70. Shona says:

    Ah, I got my mind going and cracked it. Wish I hadn’t seen the hint now, it would have made it harder.🙂

  71. Nick Sharratt says:

    With the clue that the total of each quarter should be 20, I see I have a different (but definately correct) answer as each section in my solution totals 19 instead.

    Will ponder how to get 20 as total instead-think I see it already, just need to check…

    • Nick Sharratt says:

      Yep, I now have an equally valid solution for 20 in each quarter too using the same idea. Pity really as I liked this puzzle and disappointed now that it actually has multiple solutions. Makes it less ‘pure’ and satisfying to solve.

  72. Eddy says:

    About 3 minutes for the first solution, but it seemed rather ugly and inelegant (though definitely valid). Second solution took another minute or two and I’m pretty sure is the one Richard had in mind.

  73. Seal says:

    after seeing the clue it took about 2 minutes

  74. cole says:

    doh, i drew a clock to work this out, id be there all day until there was mention of ‘the trick’ and noted down exactly what was on screen then it was easy

  75. Fraser says:

    Oooh sneaky. Got it, 4 mins?

  76. Francesca says:

    SOLVED IT! Finally! So happy! ^^
    I had to use the clue though, since I spent quite a lot of time poring over the puzzle last night and didn’t get it at all. Feeling rather accomplished now, having figured it out eventually rather than not at all. (:

  77. bw says:

    Warning to non-native English speakers: there is a word in the question which does not mean what you may think it means. This is crucial to the solution. Moreover, Pr Wiseman himself is sloppy about this crucial point in the statement of the question. So if you can’t do it, don’t worry, it’s just a trick question with a very simple solution (once I understood the question correctly, it took me 2 min).

    • As someone interested in linguistics as well as puzzles, I am curious as to which word you have in mind, and why you think it’s particularly likely to confuse non-native speakers. I hope that you’ll reveal all after the solution is posted.

    • lakritze says:

      I’m not a native speaker either, and I still don’t know what you’re talking about, bw. To me the question was perfectly clear. Now I’m curious about your mother tongue.

  78. Julia says:

    As usual, I was thinking far too laterally. With the clue it became very easy.

    ps: as a non-native speaker, I’ve got to say that I have no idea what bw is talking about. Sorry, bw.

  79. Carl says:

    Great puzzle. Realized the gimmick quite quickly, but took quite a few mins to fully solve it. There’s 2 or 3 logical hoops you have to jump through, which I think is what made this puzzle so much fun.

  80. Wayne says:

    Managed it in about 10 mins, should have been sooner but I was aiming for the wrong number at first. Der der.

  81. john says:

    took like 5 sec.

  82. Rex says:

    At first I got an answer but wasn’t sure about it, but after seeing the hint I”m pretty sure I got it right.

  83. Ms G says:

    Ahaha .. that’s not nice .. have us staring at the numbers whereas you meant ofcourse not those numbers but the little twist in that sentence ..
    a little brain screwer .. I’m not zoning out here right now .. trust me .. checking into my most superb hidden brain underneath .. check for schemes in richard’s questions .. man of little mind tricks ..

  84. Paul says:

    About 5 sec to spot there would be a trick, another min to spot there would be a second trick, and about 5 mins to solve it. Then another 5 mins wiping my fingerprints off the screen ‘cos if my wife found out I’d been rubbing my grubby paws on her laptop I’d be typing this from the afterlife!

  85. KateKatV says:

    Immediately suspected the numerals as opposed to numbers were important … took about 5 minutes to realise no need for all cuts to be to the centre (nice touch that, the + in the middle) … decided I needed to draw it out, couldn’t be bothered, forgot it … cleaning teeth this morning and the solution popped into my head, all complete … subliminal processing !!!


  87. Nobody says:

    i dont wanna figure it out yet. : )

  88. Yong says:

    So beautiful! I like the earthy & classic tones on the wedding! I’m so stealing the succulent idea. Lovely bride, handsome hubby & bridal party. Amazing footage as often Tammy!

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