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Please settle this argument...

  • 10-10-2009 05:01PM
    #1
    Gholimoli
    Registered Users, Registered Users 2 Posts: 3,450 ✭✭✭


    folks,
    i had this argument with a friend of mine last nite.
    its basically a probability question and he said that it was posted on boards some time last year.

    The Question
    we are in a TV show and we have 3 boxes.
    box number 1,2,3.

    there is $1 mil in one of the boxes and the presenter asks us to pick a box.
    if we pick the box with the money in it ,we win the money.

    so we pick box number 1 for example.
    then the presenter opens box number 3 and it's empty.

    he then asks us if we want to stay with our original choice(which was box 1) or do we want to change our pick to box 2.


    My Answer
    well my answer was that it makes no odds whether you change or not.
    essentially you have now 50/50 chance of winning the money and thus there is no difference between them.

    My Friends Answer
    my friend says that there is a huge difference between the boxes and that we should change our pic to box 2.
    he said something like at the start ,when we have 3 boxes ,there is 33.3% chance of each box having the money,which i agree with.

    he then said something really rediculouse ,which is,that after the third box is eliminated then,the first box still had 33.3% chance of having the money but the second box now has 50%.

    now this can never be ,i know this for a fact cuz 33.3% + 50%=83.3% .
    it total should equal 100% always as money is deffo some where under one of the boxes.

    when you eliminate the third box ,the 33.3% of that box gets distributed between the other two boxes,making the chance of each box having the money eqwual to 50%.

    the only thing i can think of ,is that maybe somehow magically ,after the third box is eliminated then,the second box gets the entire equity of the third box leaving the percentages like this : Box1=33.3% Box2=67.7% .
    i dont see any reason for this but my friend insisted that he has seen the proof on boards abt a year a go so can you please settle this for us.

    thanks.


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