It’s the Friday Puzzle!


First, on Monday I am giving a public talk at the University of Hertfordshire about the paranormal on film….and it is free!  Hope you can make it – details here.  OK, to the puzzle…..

I have decided to hold a Mouse Clicking Competition.  So far, there are only three entrants – John, James and Jack.  John can click a mouse 10 times in 10 seconds. James can click a mouse 20 times in 20 seconds. Jack can click a mouse 5 times in 5 seconds. In my competition, the timing period begins with the first mouse click and ends with the final click. Which one of these entrants would be the first to complete 40 clicks?

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

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for theKindle (UK here and USA here) and on the iBookstore (UK here in the USAhere). You can try 101 of the puzzles for free here.


91 comments on “It’s the Friday Puzzle!

  1. lostguru says:

    if i’ve interpreted this problem correctly, i think i got it (time 2 minutes)

  2. Simon Taylor says:

    Took less tha 5 seconds to work out!

  3. CH23 says:

    I have the feeling i’m trying too hard to solve this.

  4. Michael Sternberg says:

    It clicked here after a few seconds, and a few more to be sure.

  5. John Loony says:

    About 10 seconds.

  6. Roland says:

    Nice 🙂 Assuming that the click speed can be kept up after the specified period per person 😉

    • Berhard says:

      Jup… but it would also work with “automated click – machines”…

      Took me a few seconds to have the “most probable” solution under the most likely assumptions..

  7. Pete says:

    I had an intuitive answer straight away but then took about 1 min doing the maths to prove it

  8. Ale says:

    I got it right after finishing reading… Mmmh, I guess I must be wrong because it was way too fast compared to every other puzzle I tried.

  9. Damocles says:

    Meh, got, easy. Won’t bother with the maths, I have a train to catch (you have to run quite fast, they’re speedy things).

  10. lehcyfer says:

    Is that a puzzle? I couldn’t find anything puzzling in it…

  11. Kristian says:

    I never really liked fence poles. 3-4 minutesish all in all.

  12. Hugh Janus says:

    Another vveery easy one. Took me 0.006 seconds before it clicked.

  13. Niva says:

    It took about 10 secs, about the amount of time to read the puzzle. I wonder what people are doing who are taking minutes to solve. 🙂

    • Kristian says:

      I did the math for each of them, took a couple of minutes.

    • Niva says:

      OK, I recant my previous post. After thinking more about what’s needed to generate a click, another answer (which I’m sure is the intended correct answer) makes more sense. It does, however, require an assumption that’s not explicitly given in the problem statement.

  14. Charlie says:

    I don’t always get the asnwer straight away (e.g. the Boston-NY train), but like Lehcyfer, I can’t see any puzzle or lateral thinking required for this one. So much so, I suspect there must be more to it and my answer is wrong.

  15. Rob B. says:

    I don’t believe the obvious answer is the right answer, but I think I’ve worked it out.

  16. Nigel says:

    What’s the puzzle? I’m sure I’m missing something here.!

  17. Anonymous says:

    Took a few seconds to engage mind, a few more to arrive at an instinctive answer, and a few more to check the maths. Today, I’m officially good!

  18. edgar1975 says:

    It looks too easy… I mean, not like a puzzle at all 😦

  19. Monty Hall says:

    Took me exactly 40 seconds to do it. Just like everyone else.

  20. Tom Cantwell says:

    Very easy, but how did John, James and Jack ever find out that they could only do that amount of clicks? And where was ‘forty-click’ Jerry when he was needed?

  21. So much depends on the assumptions you make 🙂 Seemed so much “not a puzzle” until you look.

    Obvious – and flawed solution – after reading.

    Highly probable right solution – a couple of minutes.

  22. Stu says:

    I agree with serverdude – anyone solving this in under a second or two has DEFINITELY got the wrong answer. The right answer – when you find it – will show very definite first, second, and third places for the three clickers.

  23. Beaky says:

    Almost instantaneous. Then 20 secs to make SURE. Yep, I was right.

  24. The Masked Twit says:

    Has anyone else noticed that John can click a mouse 5 times in 5 seconds too?
    Gosh – I’ve just noticed that James can as well…..
    I haven’t actually “solved” it as I’m not very good at semantics.

  25. safc4ever says:

    About 60 seconds of thinking spread out over a couple of minutes, in batches of 4*5s, 2*10s and 1 of 20s.

    Seriously, though, it was clear that the fastest person’s names begins with J

  26. Martin says:

    Yes, this is not as obvious as you might think… there is a definite 1st, 2nd and 3rd.

  27. Merari says:

    presumably less than a minute

  28. Clare says:

    I twigged the answer in a couple of seconds but then spent about five minutes checking it to see if it was based in any fact. It was : )

  29. Richard says:

    Had an instinctive answer which popped into my head immediately on reading the question. Wasn’t sure why that was my instinct though, so I did the maths. It was right after all, so you could either say “immediately” or “5 minutes” as to how long it took.

  30. Gut feeling: seconds, working it out on a piece of paper: 1 minute

  31. Martin says:

    Here’s one. How many times can Jack click the mouse in 10 seconds?

  32. M says:

    Took a while before I understood the question. (30 seconds) Slowly I understood what was going on (10 seconds) then I got the answer (5 seconds). So it took me less then a minute.

    By the way, I’d win from these three entrants easily.

  33. Anonymous says:

    I don’t get it at all. That took me about 30 seconds to decide.

  34. Peof says:

    I simply don’t get it!!! I thought I had the solution until I read they had a specific winner… Help?!?

  35. Jerry says:

    I’m a little worried that some people are doing maths, simple division aside, it’s not called for in my solution.

  36. Pedro says:

    It takes me 5 minutes to give the solution to 5 puzzles, but I cannot solve 5 puzzles in five minutes.

  37. Hendrik says:

    it took me about 20 secs, funny semantical thinking!

  38. Wolf Martinus says:

    took me 37.05 seconds

  39. Anonymosity says:

    Obvious answer came while I was reading the question.
    Correct answer took a few seconds longer.

  40. deepfield says:

    Had to read the hints, and then about 40 seconds to do the maths.

  41. Matt says:

    As far as I can tell, this can’t be answered. I get that from this we gather that 5 clicks in 5 seconds isn’t one click per second, so Jack’s click rate is either just slower or just faster than that. If given 6 seconds he might be able to squeeze in a 7th click, or he might not make that 6th click before the 6 seconds ends.
    All I can gather is that there is a greater margin of error with Jack, then it’s John, and James is the closest or most accurate click rate to the one-click-per-second.
    A winner can’t be deduced from this.

    • Anon says:

      Well done sir. I suggest you also tell the fence post fans where they can stick them as well.

    • Martin says:

      I think you have to make an assumption that the ‘timing period’ rule applies to the users’ measured click rates too.

  42. dmon70 says:

    2 seconds for a “duh it’s obvious” answer, another minute staring at it wondering, “is there a trick I’ve missed here?” Then 10 seconds with pen & paper.

  43. Palpatim says:

    Thanks for the hint, Kristian. It made me re-read the puzzle more carefully and realize I had made an incorrect assumption.

  44. Dribbling Sidney says:

    Answer guessed almost immediately (<5s), but another 20s to prove with calculation….(helped with the basic concept due to the fact that I had recently replaced my staircase balustrade).
    DS 🙂

  45. Are they making fences out of mice or something?

  46. Clive-twat says:

    Trick question. Mice squeak they don’t click.

  47. Typical men, it’s all about how fast you click isn’t it? No concern what you’re clicking on!

  48. Duncan says:

    I’ve got an answer and I’m pretty sure I’m right, but too many assumptions in this one for my liking.

  49. Karl Withakay says:

    Usually the key to these puzzles is to not make any assumptions and read exactly what the puzzle specifically says. Sometimes it can be helpful to write and equation or draw a diagram to describe the conditions specified.

    Too often we read something written quite clearly and make assumptions about what is says, like the assumption that timing clicks in this matter means that it takes each person 1 second to click a mouse.

    **********BIG HINT**********

    For any of the entrants, how long does one click take using the specified timing method?

    • Rob B. says:

      I second this advice. My first instinct was to draw a diagram, and that really helped me to conceptualize the true nature of the problem.

    • Anon says:

      What is the specified timing method – chronometer, stopwatch, egg-timer? It’s also so confusing.

    • Anon says:

      The words just, precisely and exactly do not appear in the question.

  50. RModule says:

    2 seconds. Just as trivial as last week 😦

    • Chakolate says:

      2 seconds is way too long. Except that I had to read it twice to make sure it really was as easy as it seemed.

  51. Walter says:

    I can click the mouse 2 times in 2 seconds, and that’s pretty lame. 🙂

  52. Lazy T says:

    Was the mouse in thursday’s picture with the cat?
    I didn’t go for the immediately obvious wrong answer I sketched out a couple of others before deciding there’s not enough info for an absolutely correct answer.

  53. Got it right away, but then took a minute to verify my answer. It is the reverse of the problem about 2 sharpshooters. One can get off 5 shots is 5 seconds; the other can get off 10 shots in 10 seconds. Which is the faster shot?

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