coverPlease do NOT post your answer, but do say if you think you have solved the puzzle and how long it took. Solution on Monday.

Find 5 identical coins.  Can you arrange them so that every coin is touching every other coin?  I will warn you now, it’s tricky!
I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.


    1. I’ve seen this before. Unless you’ve seen it before, Roland, there’s NO WAY you got it in one second. Check your answer again–is EVERY coin touching all four other coins?

  1. It’s not tricky at all. Got it in 2 seconds. I get the feeling that there’s supposed to be some sort of additional constraint if it’s supposed to be tricky.

    1. Two seconds ? I think not. Come on be more realistic with how long it took. Try timing yourself to see if you are not deluding yourself over how long it too.

  2. Ten minutes or so, using five 5p coins.

    The first ‘answer’ I got was within seconds… and it looks beautiful on paper. Unfortunately it doesn’t work with actual coins.

    So I tried with real money and it works. Good puzzle.

  3. another one where I cannot say how long it took, because it involves remembering how long it took me to read it when I first saw it. I am not absolutely certain, but I believe this is another Martin Gardner puzzle.

  4. A bit of mental wrangling to formulate possibilities, went to get a coffee, sat back down and located five 5p coins, got it in about a second. My solution is not related to the mental wrangling, so it just goes to show that sometimes you have to actually do rather than just think in order to reach a solution.

    1. I absolutely agree. My first answer failed because I did it on paper and I forgot to include a pretty basic fact about coins (which I’d better not mention in case it gives the game away). When I did it with 5p coins, it took no time at all.

  5. I looked in my wallet and found I had quite a lot of 50p pieces in it, which are 7-sided. I found a solution which worked for those in a minute or so, but which wouldn’t work for round coins, unless they were very thin. I shortly found a solution which works for round coins of variable thickness. I’m surprised at the people who solved it in a second, perhaps they have seen it or something similar before.

  6. Got it in a couple of seconds, I didn’t try to come up with an answer until I had five coins in front of me. They were similar though, not identical. 3×2 cent (euro)coins 1 old Irish penny ( the rally small ones) and an american cent.

  7. that was interesting. i had never seen this puzzle before and it gave me some trouble at first. but after playing with 5 pennies i managed to get a solution within a minute or two.

    i’m curious whether the solution i found is unique.

  8. I find puzzles I’ve seen before much easier to solve than unfamiliar puzzles. (This is my way of saying “easy, 1 second”. I can’t help but wonder if those who claim it took them no time at all to solve a puzzle were already familiar with it in the first place.)

  9. with 5 x 1p and a bit of blutac I thought I had a solution in a couple of minutes, but then looked more closely and realised there was a gap!

  10. I think I’ve got an answer, but only in theory – it doesn’t work when I try to do it for real using 2p coins.

  11. Couldn’t get my head round it until I located coins and tried a couple of ideas. Took probably about 20seconds to work it out. Just bit of lateral thinking and common sense this one.

  12. 30 seconds or so. Quickly realized the basis of the solution, tried one solution mentally, saw the flaw in it, and then realized the real solution. Pretty fun puzzle. The lateral thinking came easy enough having tried enough of these, but I’d never seen this one before, so I got to feel like doing these puzzles is actually improving my ability to apply the skills to new problems. But maybe it was just easy and I should stop feeling so proud of myself.

  13. If you solved this in less than a minute (and haven’t seen it before), check your answer again. Are you sure that EVERY coin touches all four other coins? As Richard says, the answer is tricky.

    1. Having done it with actual coins it was easy to check they all touched. Took a bit of rearranging and may well be that there’s more than one way of doing it but definitely got all coins touching each other and not that tricky.

  14. I think the question should read “.. so that each coin touches all the other coins”. “Every other coin” sounds like you’re skipping a coin in between. Just saying.

  15. Longer than I would care to say.
    At first I Googled it just to check that there was a valid answer (but didn’t look at the answer).
    For those people that solved it in 10 seconds or less – what are you doing wasting your time on this site when you could be saving the world with your impressive brains?

  16. for those who are curious, or just can’t help themselves, it is worth noting that if you google the answer, the most common answer provided is in fact wrong. it may look good on paper, but if you actually get the coins out to try it, it won’t work. it’s very hard to hold the coins so that they are stable enough to see the gaps, but they are there.

    1. ctj
      If you are saying that it is nigh on impossible to do this via the answer commonly shown on Google without glue, Sellotape, bluetack or similar I would tend to agree.
      If you are saying that the common Google answer is theoretically incorrect I disagree. I have done it (with Selotape) and there are no gaps.
      I look forward to seeing your alternative solution on Monday.

  17. i spend 5 mins with five similar coins (nb not identical, have different years).

    i find soln to puzz, i think. very satisfactory.

    but what if my soln is wrong? i now spent whole weekend not solving puzz because i have no way of to check the soln.

    mr richmond does not allow publish our solns, so all we can do is think we are right. would be better if we had some way of having solns checked.

  18. I spent about 5 minutes fiddling with 5 £1 coins.
    Then I gave up and read through the comments, hoping to find a clue.
    I’m still baffled.
    I will try again before I cheat by googling.
    Can I have a clue? Is it easier with thick or thin coins?

  19. Another 10 minutes of trying and fiddling. A sudden flash of insight. “Eureka!” I thought; but on fiddling carefully I think it doesn’t quite touch. If it does touch, and if I’m right, then it is probably easier with large thin coins rather than fat ones.

  20. The people saying it took them 1 second didn’t actually do it. Whatever their imagined solution was, I assure you it won’t work.

  21. I can arrange them accordingly but only if I can keep hold of the arrangement.
    I, would be interested to know if it the coins can be arranged and left alone in the same situation.

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