An easy one this week…..What caused the recent riots in Britain?  Just kidding….here it is……

Which is a better fit (i.e., results in less wasted space), a square peg in a round hole or a round peg in a square hole?

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 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. The question’s pretty ambiguous, so I’ve worked out how much space the smaller shape takes up as a percentage of the larger shape. I won’t say how, but hopefully that’s good enough as an answer.

  2. It’s ambiguous all right – took me about 5 minutes to calculate and compare ratios of area left to area of hole.

    I’d add to the question phrase: “when the round hole and square hole have identical area”

    1. When sizes of holes are equal, there is no need to calculate the ratios, but I agree – the wording is “which is a better fit (i.e., results in less wasted space)” so the size is irrelevant, only ratios matter.

  3. First is a really puzzle to me still didn`t figure it out.

    (How to control 300-500 idiots is a puzzle). However, sri lanka forces eliminated 10,000 idiots to bring peace.

    The second: 3 min

  4. 10 mins, mostly due to a schoolgirl error of mixing up my 2piR and my piR^2 ‘s!! D’oh! Suspect that’s possibly how the riots started too…! 😉

    Solved problem for “wastage as a percentage of the hole area” as agree puzzle wording a bit ambiguous.

  5. I didnt use constant peg area. I kept constant the circle diameter. Going back to do the ratio which should be independent of sizes

  6. First puzzle is just too easy.

    Seconds puzzle:

    Just visualizing it, I’ve got an answer – 30 seconds or so

    I *think* it’s right, but now to prove I’m right….

  7. Fiddling around in Excel for 12mins…

    As for the first problem – not learning how to solve one of Richard Wiseman’s problems – ups, I gave it away now, apologies.

  8. It’s not rioters or looters in Britain.

    It’s the beginning of a zombie invasion.

    You know what to do. Shop smart, shop S-Mart.
    Everybody got that?!!!

  9. it depends on the target to be achieved, —- with or without deformation and if the peg is for taking torque or shear loads…
    it may be possible that the definitons of holes may influence the result… are the holes of the same diameter or of the same area?

    When using a normalized approach, i.e. the area expressed as a fraction of the area of the hole, the … wins…
    In case the holes have the same diameter / width the … wins, too…

  10. As for the first part, my guess (at least for the looting part) is a disconnect between money and effort, making money not something that one earns, but a privilege that is either given or not given (making it feel unfair that others may have more of it). Well, that and just plain old monkey see, monkey do. Probably more of the latter. Teens are sensitive to peer pressure, after all.

    As for the second, there’s one answer that intuitively feels right. So it’s probably the other one. 😛

    1. True. When CEOs, bankers, royals, sportsmen and celebs appear to get lots of money for very little effort it becomes hard for the rest of us to accept getting little money for lots of effort.

  11. forgot to “answer” the first Question:

    First, what caused the recent riots in Britain?

    Presumably, a Butterfly flapped it’s wings in Brazil….

  12. Just when you thought there was one place left safe from political prattle 😦

    As for the actual puzzle, there’s no way to answer it without further information. Constant area? Constant width/diameter?

    1. It is solvable, you use example dimensions, then calculate ratios. The ratios will be identical no matter what dimensions you use to calculate the areas.

  13. A few minutes of doodling and fiddling with equalities gave me an answer I’m happy with on the square/circle thing.

    I don’t think the riot question will ever truly be answered….

  14. Second question, about five minutes. And I think the answer is always the same no matter how you interpret it.

    The first one is a trick question, it should be:
    “How do you stop them happening again?”

  15. The only honest answer to the first question is I don’t know, though I do look forward to the answer on Monday. Second question was easy enough, just took a while trying to remember my high school maths. Probably about 10 mins.

  16. Had an initial hunch, which was then confirmed by my math. About 5 minutes all in all.

    After reading the comments I see how the question can be ambigous (but apparently it didn’t catch my eye at first).

  17. The answer depends entirely on the size of the peg compared with the size of the hole.Presumably, either the round peg and round hole are different sizes, or the square peg and square hole are.

    1. I think you have to assume that the pegs fit the holes as well as they can be expected to. I other words, they touch the sides.

  18. I assumed that the holes would have a constant area (I assumed 1 inch square for the square one and thus one square inch for the round one) That helped the solution immensely. 5 minutes.

    As for the first question: it’s similar to a chemical reaction that requires a catalyst. Put two chemicals together and nothing, add a catalyst and ‘boom’, reaction. Put unemployed youth under economic and social stress, add booze and you just get more stress and frustration but add the catalyst of an allegedly unnecessary killing of a youth by forces of the government (translation: oppression) as the catalyst and ‘boom’. (the same can be said for the catalyst of lots of youth jammed together. Add a football match and…)

  19. No, the question is not ambiguous at all. It’s clearly worded. Size of the hole or peg doesn’t matter as it’s a ration thing. I.e how much of the hole in each case is filled up with a peg that just touches the sides.
    Took about twenty minutes with my eyes closed in the hot tub after breakfast.
    Worked out the square peg in a round hole a couple of different ways to exclude brain error.

    1. The question doesn’t actually mention ratios or proportions, which is why I called it ambiguous. It talks about “less wasted space”, which could mean less as a proportion of the volume of the peg or hole, or could equally just mean less space in absolute terms. If it was the latter, then clearly a very large square peg in a very large round hole would waste more space than a very small round peg in a very small square hole, and vice versa. But I assumed that he meant ratios too, in which case it’s pretty straightforward geometry.

  20. Clearly, the riots in London were either caused by President Obama or the Tea Party. Those are the only two choices offered by America’s pundit class, and our job is to simply believe.

    Speaking of idiots making things more difficult than they need to be, the answer to the second question is “It depends on how hard you swing the hammer.”

  21. About 90 seconds, leaving answer in a ratio of pi. Interestingly. the area not filled by the round peg in the square hole is the same ratio as the area between 4 tins packed in a square lattice arrangement. Yup. Maths is cool. And important.

  22. A few seconds to put the math together, and a minute or two to figure out the details. The problem is incompletely stated, so the solution is parametric.

  23. If you assume that the radius of the circle is the same in both situations, you can calculate it. If the radius is not the same, you can find a solution where the wasted space is identical in both situations

  24. The question is phrased vaguely and the image in the question misleads as to what the question might be getting at. It appears that what is actually being asked is “Which gives the smaller ratio of unoccupied space – drawing a circle inside a square so that it touches on all four sides, or drawing a square inside a circle so it touches on all four corners?”

  25. Hmm pretty sure I’ve seen equilateral triangle person hole covers which don’t fall down their own hole either… Which doesn’t get us anywhere with the peg problem but at least rioters wouldn’t be able to roll them at the police.

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