It’s the Friday Puzzle!


Here is the puzzle.  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.

You are all alone on a desert island and want to measure exactly 3 inches (I have no idea why, but that isn’t important right now). Unfortunately, you have only an 8.5 x 11 inch sheet of paper. How can you use it to measure exactly 3 inches?

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.


59 comments on “It’s the Friday Puzzle!

  1. Ridiculously easy once again. Let’s have some puzzles that take more than a couple of seconds to solve!

    • Dave says:

      Your solution is wrong, however.

    • Dave's Neighbor says:

      Seems pretty obvious to me:

      Mark a point 2.345207879911715 inches on one edge
      Mark a point 1.870828693386971 inches along the adjacent edge
      Draw a line between the 2 marked points. Thanks to Pythagoras, this line will be exactly 3 inches in lenghth

      (Sits back and waits for the pedants to respond)

    • -M- says:

      Yes Dave’s Neighbor. Another one would be to redefine the inch and make three of them…

    • DeepField says:

      Hey, Dave’s Neighbor, what part of “do not post your answers” was not clear enough?

    • Dave's Neighbour (on the other side says:

      Dave’s Neighbour
      How did you come up with such a simple answer?

    • Val says:

      @Deep Field: *Likes this*
      Love it! In other words, “if you can’t read instructions not to post the answer, you’re disqualified, dummy!”
      It does, however, look like an intentionally humorous, tongue-in-cheek answer to me. I would post (*only* that kind!

    • -M- says:

      Ok guys, just do realize that dave neighbours reply is not an answer. Its just silly.

  2. Eddie says:

    Done it already 🙂

  3. Dave says:

    My mate Pythagoras knows this one

  4. Pythagoras says:

    Call me a square but this is easy

  5. Paul Durrant says:

    About three seconds to get the theory and another five to work out the practicalities.

  6. Soren says:

    That was quite easy.
    It took me about a minute to solve.

  7. The Masked Twits says:

    Did it on my own, in under a minute, without help from Pythagorus or anyone else

  8. Anonymous says:

    Easy one :D. I hope there’s still a twisted answer 🙂

  9. Mick says:

    A minute or so…

  10. Simon Evans says:

    Easy. Less than 10 seconds.

  11. SofARMaths says:

    Folded this one away in a couple of minutes…

  12. Unless my maths is wrong – you can’t be exact – only approximate to 5 hundreths of an inch?

  13. Niva says:

    Very easy. My origami skills came in handy.

  14. John says:

    5 minutes – there must be many possible approaches but I am not inclined to start searching for a ‘better’ solution.

  15. Autolycus says:

    Less than 10s. Much longer afterwards trying to work out how to do it with Pythagoras’ theorem as some of the other comments suggest.

  16. Rob says:

    About a minute

  17. Anonymous says:

    I used the folding up pieces of paper method

  18. David Dredge says:

    My middle finger is exactly 3 inches long but I don’t use it as a rule.

  19. Anonymous says:

    Yep, too easy.

  20. Berhard says:

    One key question for me is just how exactly is “exaxtly”
    My solution is at least not mathematically exact, as the e.g. the thickness of the paper and the exactness of the 11 annd 8,2 both are unknown…
    less than an minute…

  21. The Moron says:

    Nice spoilers chaps – saves me the bother of posting the answer.

  22. deehants says:

    About 2 minutes with different permutations. I don’t have any letter paper here to check though 😦

  23. Hugh Janus says:

    I use to run an origami shop. It was not very successful and the business folded after 8 months

    • Plato's Uncle says:

      The shadow moved a fractio on my sundial before I had stumbled upon a solution. However, it is exact, and done without the assistance of my friend Pythagorus.

  24. Pete says:

    Less than a minute for the “exact” solution. Another minute to work out the Pythagorean approximation others mentioned.

  25. duncan says:

    About couple of minutes, with no help from anyone! I really enjoyed this one 🙂

  26. Turd says:

    got it in 3 folds

  27. The Masked Twit says:

    I hope that the Pythagorean geniuses will post their inexact answers to educate all us idiots that got a precise answer in under a minute.
    On Monday, of course.

  28. Anonymous says:

    Every friday im surprised about the mess here. All bad human characteristics appears in this place. Poor intelligent human being !

  29. Gus Snarp says:

    It depends on what you mean by “exact”, but I think I got it pretty easily, thanks to Vi Hart.

  30. teunspaans says:

    Indeed, very easy. I wonder if there is more than 1 solution?

  31. Anonymous says:

    And how can you measure three and half inches? 🙂

  32. teunspaans says:

    actually, yes, there seem to be at least 2 solutions. One with 1 and one with 2 folds.
    3,5 inch is more difficult though.

  33. Just Mike says:

    The difference of this quiz is what makes it easy.

  34. John says:

    Pretty easy. Less than 20 seconds

  35. marktmaultby says:

    What the hell’s an inch?

  36. RyderDA says:

    I took ~45 seconds to come up with an answer, and another 20 to check it. I thought myself brilliant. Then my partner came (indepentantly) came up with a totally different, much easier answer in less time.

    I am ashamed.

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