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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.

I have a cage in my garden and it contains only chickens and rabbits (I don’t really, but play along). There are 72 heads and 200 feet in the cage. How many chickens are there, and how many rabbits?

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.

70 comments

    1. One of the funniest things I’ve ever read, Janus. Well done. My rectum all but prolapsed because I was laughing so hard. You’re a comedy genius.

    1. Another *belting* one-liner, Janus. I don’t know how you manage them so consistently, week after week. Your comedy is a gift to us all.

    2. Goliath, any self respecting numbers man (or woman) uses squared note paper not lined paper. How else are you going to draw matrices and invert them, as required for this puzzle?

    1. You really do spoil it for everyone don’t you?
      I had the result after two guesses and 2/3 minutes

    2. For those who have had their enjoyment spoiled (I got it in a couple of minutes, but the way):
      Add the symbol for Time to the unit for Power, followed by the unit for electrical Current and finish with more Time. The result describes Math Genius

    3. Congratulations, Math Genius. You solved a middle school algebra problem. Check your mail. I’m sure they’re shipping the Fields Medal as I write this.

  1. 1.5 min, using simultaneous equations. I’m glad I don’t look at the comments before I try to solve the puzzle. Somebody always has to ruin it by not following directions.

    1. It’s called ‘simultaneous equations’ – yes, come back on Monday and I’m sure someone will help. Oh, by the way there are 2 more rabbits now 🙂

  2. 20 seconds for an answer then another 20 to check.it is correct.
    Then 20 seconds more to read the comments and see what other people think and to get further confirmation that I’d got it right (sigh!)

    1. I wasn’t looking for confirmation here, just for the insightful and witty comments – the confirmation found me

  3. 30 secs to do the logic in my head, and then the same to check the sums in Excel.

    In fairness this was not a new puzzle to me

    1. That’s not cheating and I the only other way I can think of doing it is trial and error. The arithmetic is easy enough that some people will be able to do it in their heads.

  4. I quickly worked out the separate equations for heads and legs, but couldn’t reconcile them down to a single unknown variable (hey, it’s been years since I last did any decent algebra!), so cheated with Excel (one column for rabbits, one column for chickens, another column to calculate heads; look down and find the numbers that correspond to 200 heads).

  5. About 30secs in my head, then around the same double-checking on paper. I am not sure whether my mental maths was based on simultaneous equations – it’s too many years ago to remember how they work!

    1. Come back and tell us on Monday how you did it. You could be using simultaneous eq’s without realising. I’d like to see any other ways of solving this.

  6. Glad I actually worked out the answer myself before flamin Maths Genius decided to ignore the request and provide spoilers! Took me about 5 mins.

    1. Did it on the toilet nothing to write with. Is it wrong to consult twitter whilst attending an evacuation? I’d say yes but I can’t be alone and the mental exercise helps.

  7. If there are only chicks and bunnies in the cage – 2min,
    if any creepie-crawlies were in there too then I failed.
    Pencil stub and gas bill envelope.

  8. Took about two or three minutes, mostly in my head, via a process of elimination (no animals were harmed in said process). Been too long since I’ve worked out anything like this using any sort of formula that I wouldn’t remember the procedure.

  9. The puzzle was a doddle but what I don’t understand is the need for spreadsheets, simultaneous equations, guesswork or even pens/pencils – it’s simple arithmetic that can be done in the head in just a couple of seconds! (Or maybe I’m the real “Maths Genius” since I can read as well 🙂 )

  10. It took a minute to go through mentally. There’s a really simple shortcut which does away with the need for equations and pens and paper.

  11. Hmph. This took me a good 7-8 minutes, mostly because I couldn’t figure out the right algebraic equation. I thought it was going to be totally easy, but the first equation I came up with was gobbledygook.

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