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Mystical Ball

  1. May 11, 2005 #1
    http://www.mysticalball.com/

    this is weird, it turned out to be quite accurate when i play with it.
    How? How they do tat? Any theory behind this?
     
  2. jcsd
  3. May 11, 2005 #2

    matthyaouw

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    Its simple maths. If you do the sum it gives you, there are realatively few answers that it can give, and all these answers are assigned the same symbol on the chart, and then brings up that symbol when you click it.

    Try working out more than one number before you click on the ball, and see if they all come up as the same symbol.
     
    Last edited: May 11, 2005
  4. May 11, 2005 #3

    DaveC426913

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    An even simpler way to root out the trick here is to try the same number several times in a row. Try doing the example (23) several times. Your answer is always 18. But do you notice anything odd? On any given try, 18 in the chart is always the symbol that appears in the ball.



    The key then is to realize that, no matter what initial number you picked, only certain answers will apply:

    Code (Text):

    99 : 9+9 = 18 : 99-18=[B]81[/B]
    98 : 9+8 = 17 : 98-17=[B]81[/B]
    97 : 9+7 = 16 : 98-16=[B]81[/B]
    96 : 9+6 = 15 : 98-15=[B]81[/B]  
    ...
    90 : 9+0 =  9 : 99-9 =[B]81[/B]
    89 : 8+9 = 17 : 89-17=[B]72[/B]
    88 : 8+8 = 16 : 88-16=[B]72[/B]
    ...
    80 : 8+0 = 8  : 80-8 =[B]72[/B]
     
    Note that both 81 and 72 are the same symbol, as are 63, 54, 45 etc. This repeats all the way down to 0.

    No matter what initial number you choose, it is going to result in one of those few special answers.
    .
     
  5. May 11, 2005 #4

    Danger

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    It's basically just a computerized version of one of the old stage 'mind-reader' tricks.
     
  6. May 11, 2005 #5

    DaveC426913

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    Uh well, sure, but that doesn't really explain anything does it? :uhh:
     
  7. May 11, 2005 #6
    Blindingly obvious. You have a two-digit number, xy in digit form. You substract the sum of the two digits,

    xy - (x + y) (xy means two digits, not multiplication)
    =(xy - y) - x
    =x0 - x
    =x * (10 - 1)
    =9 * x
    qed

    So the only possible numbers are 9, 18... 81, and they all have the same * symbol.
     
  8. May 11, 2005 #7

    Danger

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    I didn't have to explain anything. I was just elaborating upon your post. :tongue:
     
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