Posted By
JamesC
on 2007-01-09
23:38:40
|  Re: LOL maths
If you substract a two digit number XY from its reverse order 2 digit number YX, the absolute value of the result will be either one digit; always 9, (if x and y are not equal, of course), or two digits; the result's two digits Z and Q will follow this rule: Z+Q=9
That is "The Sum of Nines", an accounting trick to determine if a number has been transposed during keyboard/adding machine entry.
Where's SVS? He should know about this also....
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