Ok. I know this isn't a perl question, but I know that some of the monks here are very interessed and good att math so I thought this would be a good place fore this question.

Background:
First you take a 6 digit number and make a litteral reverse on that (345612 would be 216543). Then you take the original number and the reversed number and calculate the difference (345612 - 216543 = 129069). Then you remove a digit from the difference (remove the 6 near the end = 12909) and then calculate the sum of all the digits left (1+2+9+0+9 = 21) then you repete this stage on the result until you only get one digit left (2+1 = 3).And now comes the strange stuff. If you take 9 minus the digit you got (9 - 3) you will get the number you removed from the original difference.

NOTE: This works on any number that isn't symetric. And if you don't remove a 9.

So here comes the questions.
Why does this work?
Why do you always get the number you removed?
Is there any algorithem that makes a mathematical revers of the number?
(I only ask this becous I think it is a part of the solution)

I hope you can forgive me for posting non-perl questions.

// Martin

In reply to Math Question by Martin A

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