It’s the Friday Puzzle!



Please do NOT post your answers, but do say if you think you have solved the puzzles and how long it took. Solution on Monday.

John weights much more than 20 stone.  He goes to the shops to buy some scales, but the scales there only go up to 20 stone.  However, he comes up with a way of accurately weighing himself every day using the scales.  What was his plan?

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

52 comments on “It’s the Friday Puzzle!

  1. Zawia Saki says:

    About one second. Easy. 🙂

  2. Simon Taylor says:

    Same here, straight away.

  3. Traci says:

    I think this one is very very easy. Or I’m missing something. I suspect the latter is more likely.

  4. SofARMaths says:

    A few second thoughts.

  5. bigdoggy says:

    Immediately, but I’m wondering if there’s another solution…

  6. John Green says:

    He ‘weights’ much more than…?
    Is this part of the puzzle?

  7. The Masked Twit says:

    About ten seconds, but it would be easier to buy a set is scales which cover John’s weight range.

  8. Ajit Athle says:

    Also he goes to “the shops” — perhaps one shop is allowed to sell only one unit to a person!

  9. Walter says:

    How much is “much more”? Up to 40 stones would be easy. Up to 80 kind of quirky. Above 80 I don’t have a solution.

    • Julia says:

      I think I’ve got the same solution as you. Though I think it would actually be quite a bit trickier in practice than it appears in theory.

      Alternatively, there’s always the method my brother used to weigh his luggage when he didn’t have any scales at all.

  10. Martha says:


  11. Eddie says:

    Too easy. Sort it, Wiseman.

  12. timdowd says:

    Two Seconds 😉

  13. Tibi says:

    To spice things up: John weighs around 100 stones, and can only buy one scale.

  14. Matt Bill says:

    Yep, too easy, Richard! Solved it as soon as I read it.

  15. Well, I think I have it, but it seems too easy to really be that easy.

  16. LazyT says:

    Several solutions leap to mind but I guess he’s not planning to disembowel himself or waste the dwindling volumes of helium available so I think he’s going to pick the easy method.

  17. mittfh says:

    As long as he doesn’t weigh more than 40 stone (at which point he’d probably have problems getting to the shops, so would have to order the scales online!), I have a potential solution which is easy to implement.

  18. Timdifano says:

    I have two solutions, one will work even if he is well over 40 stones, but I guess this is unlikely as he would never have made it to the shops in the first place.

  19. Berhard says:

    found three solutions up to now, … first in few seconds the ohters a few seconds later…

  20. -M- says:

    Found three solutions. Not sure I’ve got “the” answer.

  21. What sort of a stupid question is this? Is the answer supposed to be something other that the bleeping obvious?

  22. Zbird says:

    Even I found it easy. Say my answer Monday and check with you brainy ones

  23. Physicalist says:

    I’ve got a few answers, depending on just how dedicated John is.

  24. Anonymous says:

    No problem. Just a few more supplies to get–a good friend with a strong stomach and an open calendar and some heavy-duty trash bags.

  25. Anonymous says:

    Over here weight is measured in “pounds.” (And to be even MORE convoluted, it’s abbreviated as Lbs.) I guess we’re worth our weight in British currency.

  26. Mervulon says:

    Beyond the stones, I’m thrown by all this plural ‘shops’ and ‘scales’ litany of Brittany. I’m going to drive to the store, take the elevator up, buy a scale, and bring it home in the trunk of my car. (If they have one that can handle my stones, that is!) 😉

  27. mightyhero says:

    I know how he can weigh himself.

  28. Louise says:

    My first thought was he could tie helium balloons to his arms… O dear…
    I’ve got the answer now. :-/

  29. Nick 666 says:

    Piece of cake-chops his legs off and then ways every bit individually lol

  30. Anonymous says:

    I got it in a moment.

  31. Dharmaruci says:

    there are many possible answers to this.

    one is the use the archimedes principle. weigh himself in a bath of water and then subtract the weight of the water. this is easier in metric as one kilo is the same as a liter.

    or he could do the obvious and weigh himself twice.

  32. The other Matt says:

    i definitely got two answers ! 3secs and 3mins

  33. Anonymous says:

    clue please?

    • Dharmaruci says:

      for a clue…..imagine the degenerate case where he has a scale that can only weight zero stones (or zero pounds or zero kilogrammes. in this case the conversion is easy, not like with Temperature).

      from the soln you have there now imagine he can weight to to twice his weight (not half) on a single scales purchased from the shops.

      now what is the general case? (perhaps a step is to also imagine he weights zero).

  34. Walter says:

    Found a solution where John could weigh theoretically any number of stones, let’s say 1000 stones, but this would involve A LOT of scales and I am not sure if this would statically work.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s