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Sun 4 Sep, 2005 03:31 pm
Hi all! Here's a link you all must check out:
http://digicc.com/fido/
How does this work every time???
Thanks!
Digital roots. Scrambling the digits doesn't change the digital root of the number. Therefore, the digital root of the difference is zero (a multiple of 9). Knowing that the sum of the digits is a multiple of 9 (and that 0 can't be chosen), it's easy to calculate the chosen number.
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