[at-l] This is weird

[dajones at isp.com (David A Jones)]

Bob C wrote:

>choose any two digit number ( if you write it "MN" then its numerical 
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>
>>value is M*10 + N )
>>add together both digits (M+N)
>>and then subtract the total from your original number ( (M*10 + N) - (M 
>>
>>+ N) = M*9 )
>>You should now notice that the same symbol is associated with every 
>>number divisible by 9.
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>>
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>So? When I do the test, a variety of symbols show up. I'm sure this is a math puzzle, since I don't believe in magic -- even trail magic. But I have yet to figure this out.
>
>Weary
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Regardless of which two digit number of you choose, the calculation you 
do will result in 9*M, where M stands for the most significant of the 
two digits you chose.  Every multiple of 9: 9,18,27,36,45,54,63,72,81 is 
associated with the same symbol.  (90, and 99 are red herrings, since 
the calculation will never result in these answers).  In different 
instances of the puzzle, the symbols themselves may change, but those 
associated with multiples of 9 will always be same (and agree with the 
mystical answer).