It’s the Friday Puzzle!


OK, here we go with this week’s teaser.

When Jane was just eight years old she developed a bit of a crush on Jim.  Jim was eighteen and decided to make a promise to Jane.  He carved a heart into a nearby cherry tree and placed his initials inside the heart.  The heart was out of Jane’s reach by 16 centimetres.  Jim promised to marry Jane when she was tall enough to carve her initials next to his.  Jane’s reach increased by 8 centimetres a year, but the tree was growing by 7 centimetres each year.

How old was Jane when she could ask Jim to keep his promise?

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.


92 comments on “It’s the Friday Puzzle!

  1. Craig Morgan says:

    Got it right away.

  2. Roland says:

    🙂 Nice puzzle, and it may surprise Jim

  3. Nice and easy, this one.

  4. Dave says:

    I’m calling child protection…

    • Navneeth says:

      You can’t sell your case. You can probably figure out the reason why — I don’t want to say it since it may offer a hint of sorts to those who haven’t yet solved the puzzle.

  5. Navneeth says:

    I know it has a solution. Off I go to find other things to do.

  6. Sari1967 says:

    Think I got it straight away of it is as simple as it seems

  7. Navneeth says:

    You’re actually supposed to consider how trees in puzzles grow. 😉

    • PlannedChaos says:

      Yeech. You’re right. Then again, if we’re to assume that she grows exactly 8 cm each year, every year, then this isn’t necessarily the most realistic of puzzles to begin with, so who can be exactly sure how Richard wants us to interpret it?

    • Berber Anna says:

      It doesn’t say she grows, though, just that her reach extends. Maybe he provides her with a longer stick each year? 😛

    • If it only said “she grew…” you’d ask – but what about her arms? I think its fair to say “her reach extends by 8cm / yr” to mean something like she got 4cm taller and her arms got 4 cm longer.

      And another thing! Til now everyone keeps talking about the girl or the tree….

  8. John Loony says:

    I think we haven’t been given enough information to answer the question definitively. The information given could allow for any answer between A and B, depending on what the other unstated variables are. A and B are very substantially different.

    • Luke says:

      Nope…you don’t need to be an arborealist to know that there are no unstated variables.

    • Rob J says:

      I don’t think we can really work out the definitive answer unless we know whether Jim intended to marry Jane or not. I have created a BASIC program on my commodore 64 to go through all the variables and it conclusively proves that it is inconclusive.

    • Camel Ali says:

      @ John and Rob.

      LOL. Nice one.

  9. Merari says:

    < a minute

  10. JimC says:

    This seems to be straightforward, so obviously I’m missing something.

  11. RobHes says:

    I’ve heard this one before, so even before I finished reading it. But it is a good one

  12. StewE17 says:

    Got it in one minute.

  13. koldito says:

    The age is irrelevant, the important fact is that she would have been freakishly tall. Jerry would have been marrying a giantess.

  14. M says:

    Nice one! It’s tricky

  15. Eddy says:

    Got it in about 15 seconds, AND learnt something new — good start to the day! 🙂

  16. Stuart says:

    I’ve got an answer. Don’t know if it’s right, and it took me about a minute

  17. Tom Pedersen says:

    10 seconds, then I remembered a fact about trees, so 10 more seconds after that.

  18. Emlyn says:

    Seems extremely easy, is there a twist that I’m missing?

  19. marie says:

    2 seconds

  20. Mathlete says:

    In order to answer we need to know at how much length Jim has craved the heart and total length of tree at the time of craving considering the tree will grow in equal proportion..

  21. Well there’s the obvious answer but it took a few seconds to realise that had some rediculous consequences so that left another answer But then another suposition occurred to me as I read the first comment. Now I seem to be in agreement with others here in less than a minute.

  22. Mickey D says:

    Got it affter thinking in the shower, so about 5 mins.

  23. Anonymous says:

    I have three possible anwsers:-
    a. 1/5
    b. I didn’t read the question properly
    c. Jim is gay

  24. Jenifer says:

    Got it straight away. 😀
    It’s nice to have an easy one sometimes.

  25. Berber Anna says:

    Eh. Either this puzzle isn’t, ahem, rooted in reality, or the solution is rather creepy.

  26. Nanda says:

    Nice story than puzzle. good for thanksgiving

  27. Gilly says:

    I found the equations for each growth, and set them equal. Solve for age. Fun easy puzzle.

  28. Kitty says:

    It’s not an unrealistic puzzle. I also gain 8cm of reach every year. I could reach my dad’s nose when I was 8, now I can put my elbow in a basketball hoop. How old am I?

  29. vaahto says:

    There’s some missing information about the season when the puzzle happens. It could make a quite significant difference to the answer.

  30. Tony says:

    As always there’s a twist in the tale… Thought I had it then realised I didn’t then discovered the key to the solution. There is one. It’s not hard.

  31. Steve Jones says:

    Is this a question about maths or botany? Whichever it is, one or the other of these two is in either legal or physiological trouble.

  32. TS says:

    Got it while reading the post.

    I’m thinking that Jim and Jane are from the deep south in USA…

  33. Prateek says:

    She had always been a happy child. That was, of course, before the Spurt.

    Her friends were astonished, her doctors; puzzled. Not only was she outgrowing her peers at a phenomenal pace, she was doing so at an eerily constant rate as well.

    “8 centimeters, every year, since the age of 8. No exceptions,’ Dr. Ramprakash muttered to himself, trying desperately to make sense of the unwaveringly linear graph propped up against the wall.

    Her Vietnamese parents were over the moon. For centuries, their bloodline had ensured that not a single individual had any reason to be annoyed be low-lying doorways. “We’re both very proud of Jane,” beamed her doting mother, “Finally, I don’t have to climb up on to the counter to reach the cumin.”

    Jane herself was less than enthused. “None of the boys will even look at me. I feel like some kind of a monster,” she scribbled in her diary, on the eve of her sixteenth birthday. She cried herself to sleep that night, the extremities of her 6 foot 3 inch frame dangling wearily off the edge of her bed.

    She’d never quite gotten over Jim either. “Maybe, just maybe”, she thought to herself on particularly malevolent days, “I’d have forgotten about him by now if he hadn’t made all those pathetic promises.” It didn’t help that his newly-wedded bride was a gorgeous, petite lady who she dreamed of crushing under her ridiculously large feet.

    Ramprakash had thrown in the towel over a year ago. In fact, not a single medical expert had the faintest intuition. Every scan, every test and every fancy-schmansy diagnostic machine had come up blank. Jane continued to grow, and wallow in woe.

    She died peacefully in anguish, some years later. Her sullen corpse, too large for a standard coffin, was left out for the vultures.

    Her story, sadly, has been resigned to near-obscurity. But every now and then it appears fleetingly on the interwebs; quoted by Wise men as riddles in a rather more watered-down context.

  34. Chris says:

    Easy once you forget about the maths.

  35. Lyndon says:

    The next day, when she went to store and bought 16 centimetres tall stool. Jim had legal issues though, Jane bing only 8.

  36. A couple of minutes lateral thinking then a further reading of the question and an answer that I think I might be debating with others on Monday. My answer is very specifically influenced by what Jim promises! It requires no arboreal knowledge.

  37. Martin says:

    1 min to understand the question and draw a diagram.
    10 secs to come up with a mathematical answer.
    1 min to find a ‘real world’ (England and Wales) solution !

  38. Vegar says:

    10 minutes of writing a simulation as a perl exercise and concluding that they will have a fine marriage.
    Then 3 hours wondering what I missed.
    2 minutes of reading comments.
    1 minute of facepalming.
    1 minute of rewriting the silly perl script just for spite.
    3 hours 14 minutes.

  39. Mad Kev says:

    This isn’t a puzzle, it’s primary school maths. Embarrassing.

  40. Lazy T says:

    I think that if you carve an heart into a tree you’ve married it,

  41. mittfh says:

    A couple of seconds to do the primary school maths equation. A few more seconds (after reading the comments about tree growth) to realise I’d made an obvious error and revise it to something far more achievable (albeit causing a few legal problems!). A few more seconds to realise another fallacy with answer (1) – this time related to how humans grow…

    Answer 1) He’s got the patience of a saint
    Answer 2) Far quicker, but there’d be legal implications
    Answer 3) He’ll remain a batchelor for life, unless…
    Answer 4) She buys a chainsaw or there’s a hurricane 🙂

  42. Alexandra says:

    At first I thought I got it straight away, then took a moment of going through the math equation I wrote down to realise my mistake. It’s quite funny to miss something that obvious 🙂

  43. Paul Durrant says:

    A puzzle that requires a bit of natural history as well as arithmetic!

  44. Paul says:

    Hmmmm…two answers. Not sure on the right one. If one of them is even right at all. Got it in 30 seconds. So probably both are wrong.

  45. Wolf Martinus says:

    Thanks to her ladderal problem solving skills Jane found a very quick solution to the problem.

  46. Todio says:

    Immediately. Had a fun science teacher who posed a similar question as a bonus point on an exam.

  47. Bang a nail in a tree and watch

  48. Antonio says:

    I arrived to a solution in 10 minutes, it is logical in maths but not in implications…

    See you monday guys.

  49. Hal Harris says:

    This one was easy.

  50. Anders says:


  51. Jerry says:

    A friend of mine and I came up with two possible answers depending on how trees grow.

  52. Dee says:

    It depends what country they’re in… 🙂

  53. One Eyed Jack says:

    Jim is a pedophile.

    Any other answer shows a profound ignorance of how trees grow.

    • John Loony says:

      I am profoundly ignorant about how trees grow, and so are probably most people in this thread. That’s what makes it interesting.

    • Carl says:

      Maybe John was just profoundly ignorant of how trees grow. He’ll have plenty of time to brush up on his botany from his jail cell.

  54. One Eyed Jack says:

    There is a second answer based on language semantics, but I find nit-picking grammar to be fairly lame as brain teasers go. Either way, Jim is still a pedo.

  55. Sili says:

    Sounds like the exercise with the worm crawling out of the well, but while that one is tricky because of the discontinuity, I can’t decide if that applies here, too.

    I assume that trees only actually grow in part of the year, but I don’t know if human growth is continuous or not.

  56. John Loony says:

    Page 112 of the 7th edition (1989) of the Guinness Book of Answers says that the average 8-year-old girl grows from 77.5% of her eventual adult height to 80.7% in one year.

    Assuming that this annual growth of 3.2% is 8 centimetres, and assuming that Jane’s growth rate is the same (as a proportion of adult height) as the average girl, then Jane’s eventual adult height will be 2.50 metres (8′ 2½”), and at the age of 8 she is already 1.94 metres (6′ 4½”) tall. So how the **** tall is Jim already?

  57. Kristian says:

    Found quite a few answers escaping the riddle with silly answers, but I think I got the intended answer. My initial solving took a couple of minutes. Confirming via wiki took 10-15 minutes. I liked the puzzle 🙂

  58. Dave Rickey says:

    Two solutions, one of which might involve the authorities depending on how tall the tree was when this started. About 1 minute to see the second.


  59. D says:

    Seems like you need to have a knowledge in dendrology to answer this puzzle.

  60. FrankN.Stein says:

    Jim might have a problem there…………….

  61. becca says:

    I know the answer, it took me a few minutes and I thought it would take me ages!
    By the way, I watched you on friday at the conference in London, it was amazing ( i was the first one to have a picture with you, in the checkered shirt haha) 🙂

  62. I wonder if it includes the female growth spurt? Anyway, as soon as she’s 16 she can go on Jeremy Kyle and get it sorted that way, no need to worry about the tree.

  63. Mort says:

    Took me about 10 seconds for my answer. Then I read the comments and realized the community of botanists was thinking the same as I was me.

  64. saudade11 says:

    The tree grow on top. The carving is on the trunk. It doesn’t move up. So the trees growing rate is irrelevant

  65. Suzy M says:

    Depends on whether Jim could afford to get married after harming the tree, being fined under the relevant legislation, battling the EDO in court and having to restore several acres of land as recompense – sigh….
    Apart from that – a minute or so.

  66. all sports games…

    […]It’s the Friday Puzzle! « Richard Wiseman[…]…

  67. Ethel says:

    Awfully enlightening many many thanks, It appears to be like like your current readers could possibly want even more blog posts similar to this continue the terrific effort.

  68. lavacabezas portatil granada

  69. illinois flat fee mls rental listing

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