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Creative (lateral) thinking to solve a complex problem

  1. Sep 27, 2004 #1
    A merchant owed a large sum of money to a moneylender. The old, ugly moneylender fancied the merchant's beautiful daughter. He proposed that he would forget the debt if he could marry the merchant's daughter.

    The merchant and his daughter were horrified. The cunning moneylender suggested that they let providence decide the matter. He told them that he would put a black pebble and a white pebble into an empty bag. The girl would have to pick a pebble from the bag.

    If she picked the black pebble she would have to marry the moneylender and the debt would be forgotten. If she picked the white pebble, she need not marry him, and the debt would be forgotten. If she refused to pick a pebble, the merchant would have to go to jail.

    The moneylender bent over and picked up two pebbles. The sharp-eyed girl noticed that he had picked up two black pebbles and put them into the bag. He then asked the girl to pick her pebble from the bag.

    On first impression it would seem there were only these possibilities: 1) she refuse to take a pebble, 2) she show that there were two black pebbles exposing the cheating moneylender, 3) she pick a black pebble and sacrifice herself for her father's debt.

    Before you read the answer, below, let us see if you can figure out a solution to this problem.

    There is one.

    The girl nerviously picked a pebble out of the bag, fumbling and dropped it on the ground so that it couldn't be known what color it was. She then said: "Oh I'm so foolish, but never mind, we can look in the bag and see the color of the pebble that is left and we will know what color my pebble was."

    Don't think there is not a wise solution!
  2. jcsd
  3. Sep 27, 2004 #2
    hehe, pretty nice. :tongue2:
  4. Sep 27, 2004 #3
    Sounds like 1+1=0 :rolleyes:

    Oh, there is "one" to carry after that etaoin's addition.
  5. Sep 28, 2004 #4
    Personally, I think Solution 2 is the best one because it removes the arbitrary "dropping a pebble on the ground so that we cant tell what it was..." There's too much at stake for that type of solution to be rationally implemented. Of course, she could just pick the one of the pebbles out of the bag, and rather than open her hand, just have them look in the bag to determine what pebble she has. Although, forcing the moneylender to explain his cheating in sight of her father is probably the most cunning.

    Oh well...situational teaser...
  6. Sep 28, 2004 #5
    Nice replies!

    I hadn't thought of how it might be good to expose the moneylender!

    You make me think, perhaps she should take a pebble, then tease by saying "I don't want you to see it!" and encourage her father to look in the bag himself.. this would at least make the moneylender have to be exposed without the girl dropping hers.

    If the moneylender is such a cheat though, it might have been best the way she did it so that he is not "exposed."

    Thanks for the great replies guys! :rofl:
  7. Sep 29, 2004 #6
    hey you should have given us a chance to think over it before giving the reply. you know if the answer is right in front then it is not possible for any normal human being to ignore it and think for the solution to the same problem.

    anyways, it was a nice one, and however hard i would have tried, i would have not thought of this answer.
  8. Sep 29, 2004 #7
    If it happened today in US.The girl will expose the fraud and sue the merchant for a couple of million $$.
  9. Oct 16, 2004 #8
    There are too many possible variables within this situation. Including; The girl could have inserted a white stone in her hand before sticking it into the bag to select a stone.
  10. Oct 17, 2004 #9
    Over optimistic!

    If this moneylender is the cheat he seems to be, don't you think he'd have pebble cheat games for the court too? Just because some people make outrageous lawsuite doesn't mean that regular folk can afford big legal cases!

    Withdrawn, nice idea, PALMING as a solution... but you assume she had time to gather a white pebble!

    Re-thinking this problem, I think sharp eyed attractive girl did the perfect thing, PLAYING DUMB in order to alleviate all kinds of unfair doings. Smart playing dumb is a great trick.
  11. Oct 17, 2004 #10
    bravo!!! :approve:
  12. Oct 30, 2004 #11
    I really enjoyed the solution to this problem when I first read about it in Mr. de Bono's writings. I know I would never come up with such a creative solution. How do you suppose the young woman might have arrived at such a brilliant solution? Have you ever seen something similar in real life or in physics?
    I love it when a plan comes together!

    Paul Sloan's series of books on lateral thinking are great!

    The man who coined the phrase 'lateral thinking' was Edward de Bono.
    Last edited by a moderator: Apr 21, 2017
  13. Nov 6, 2004 #12


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    Yeah, I didn't know the last part was the answer until I read it, I thought it was part of the puzzle... and that was a very good one, It would've taken me a while to figure it out.
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