It’s the Friday Puzzle!

51

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

A carpenter is paid 2 pounds for each day that he works and forfeits 3 pounds for each day that he doesn’t work. After 30 days he has paid out exactly as much as he has received. How many days did he work?

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.

51 comments on “It’s the Friday Puzzle!

  1. kroketje says:

    30 seconds……. again an easy one🙂

  2. Stan says:

    About 15 seconds.

  3. Roland says:

    Took me as many seconds as number of days the carpenter had to work🙂

  4. 1 min. I like a bit of maths on a Friday morning.

  5. Eddie says:

    Two easy.

  6. ChrisR says:

    10 seconds of mental attempt before deciding to go for 20 seconds on paper. Then another 30 seconds deciding whether or not some might think this post is a spoiler. Which it isn’t. Or is it?

  7. Anne Elk says:

    About two minutes. Good puzzle for my level of Maths.

  8. Anonymous says:

    easy, the obvious answer is… hey! mr carpenter what are you doing with this hammer? No! No!…

  9. The Masked Twit says:

    Took me about 15 seconds using trial and error.

  10. pen and paper, 30 seconds

  11. safc4ever says:

    Two pounds per day? Call the Union now. The Carpenter needs someone to fight for his right to be paid at least the National Minimum Wage!

    PS. It took about a minute. I could have done it quicker but my brain was still in “Union Leader on Holiday” mode.

    • mgm75 says:

      No, it’s ok. He’s on the new Tory apprenticeship schemes. They couldn’t get him into Poundland.

    • Lazy T says:

      He would be better off with one of those new fangled zero hours contracts. I imagine he’s liberating the boss’s power tools, one piece at a time and it didn’t cost him a dime.

    • Ed Wilson says:

      I was more concerned by the seven-day weeks.

      About a minute.

  12. mgm75 says:

    Oh, that was an easy one… 5 seconds – but then I probably worked it out a different way from others. Will be good to see everyone’s working on Monday

  13. Couple of minutes. Too idle to get up & fetch paper so used Educreations

  14. Baker's Dozen says:

    Does that include VAT? They always sting you with that at the last moment.

    • Stewart says:

      No, carpenters always demand to be paid in cash with no VAT receipt (or any guarantee for the work).

  15. mittfh says:

    About half a minute or so using trial and error (although if I’d been thinking hard enough, I’m sure I could have used simultaneous equations).

    Even if this puzzle dates back several decades (when £2/day was equivalent to about £200/day), being fined time and a half for non-working suggests he’s being exploited. Being a carpenter, you’d expect him to have a decent grasp of mathematics, so perhaps there’s more to his contract than meets the eye?🙂

  16. photon says:

    Less than a minute, but then I am at the bottom of a bottle of red! (& the carpenter really needs to contact the union!)

  17. avernl says:

    Took the mathematical approach. I think it took me about two minutes to solve it.

  18. jjbrinner says:

    less than one minute. ciao

  19. About 2 seconds to work out the answer, then c.15 seconds to write down the equation to check that I had done it correctly. But I didn’t see the gorilla.

  20. Stewart says:

    About two thirds of a minute.

  21. Barry Goddard says:

    I think this depends on weather he works and/or is fined on weekends. Plus weather what day of the week the first monday of the month is, Without that knowledge, we cannot solve

    • ctj says:

      it may also depend on the whether on the days he doesn’t work.

    • Barry Goddard says:

      Thank you CTJ. That too.

      It is not enough that we make all the ass-u-me assumptions of what is in Richard’s mind when he wrote the Puzzle. We must root it in the real world for the benefit of those who solve it next.

    • I Luv Introducing Ambiguities That Are Not In The Original Question says:

      Or you could just read the fracking question and answer it Barry – or is that just too hard for you?

  22. Louise says:

    Less than a minute, with a bit of trial and error.

  23. Anonymous says:

    less than 5 minutes

  24. Matt says:

    About a minute using the magic of algebra.

    -Matt

  25. Anonymous says:

    About 6 hours and 34 minutes

  26. Niva says:

    Too easy. So easy you can do the algebra in your head.

  27. jean philippe from Paris says:

    I like Friday Puzzles… you keep practising simple simutaneous equations, and then you get the answer immediately thanks to Dave…
    Beware, Richard is watching us like lab rats. If not, he would easily be able to ban spoilers.

  28. Nitwit says:

    2x-3y=0, x+y=30, or y=30-x, so 2x-90-3x=0 5x=90 x=18, y=12 also, graphically, the 2 lines specified by the first 2 equations intersect at (18,12)

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  30. Anonymous says:

    thank you to make work the brains of our children

  31. alain b says:

    nitwit – I comprises 2x-3y = 0, x + y = 30 or y = 30-x,
    but after how is you find so 2x-90-3x=0

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