Anyone up for math?

# Thread: Anyone up for math?

1. Senior Member
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Dec 1969
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2,958

## Anyone up for math?

Anyone explain how this works mathematically?<BR><BR>http://digicc.com/fido/

2. Senior Member
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Dec 1969
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## Scott Mitchell is probably the best....

One to look to for an actual explaination as to why it works. (He&#039;s a math whiz)<BR><BR>But, for an easy way to solve the puzzle, programmatically.<BR><BR>When you subtract a number from its inverse (assuming the remainder isn&#039;t zero) it&#039;ll be a multiple of nine. Take a non-zero digit away. <BR><BR>Say, 781 - 187 = 594 could give you 45, or 59, or 94....<BR><BR>Whatever two digits you pick, append every integer from 1 through 9 to the end, and the one (and there will only be one) that is evenly divisible by nine is the missing digit. <BR><BR><BR>So, if we take away the five, (and reverse the remaining digits, for good measure) we get 49.<BR><BR>491 / 9 = 54.55555556<BR>492 / 9 = 54.66666667<BR>493 / 9 = 54.77777778<BR>494 / 9 = 54.88888889<BR>495 / 9 = 55<BR>496 / 9 = 55.11111111<BR>497 / 9 = 55.22222222<BR>498 / 9 = 55.33333333<BR>499 / 9 = 55.44444444<BR><BR>See? 5 is the missing digit. <BR><BR>Again, Scott can likely give you the fomula, but this is my hack application. Works every time.<BR><BR>Cheers,<BR><BR>Xander

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## Or, come to think of it, Bill Wilkinson...

Got his degree in math. <BR><BR>He probably knows the real answer as well.

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## LOL

You&#039;rs works just fine.<BR><BR>It was fun trying to figure it out. I came to a not so elegant solution as yours.<BR><BR>It would be fun to see Scott&#039;s or Bill&#039;s more mathematical though huh?

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## RE: LOL

http://www.aspmessageboard.com/forum/social.asp?M=630138&F=40&P=1

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## As Dutch said...

...we discussed this to death a while back.<BR><BR>And you don&#039;t have to look for the one that is divisible by 9; you just have to find the digit that you can add to make the sum of the digits be a multiple of 9.<BR><BR>So starting from<BR> 49<BR>it&#039;s easy to see you can ignore the 9 and then you just add a 5 to 4 to get 9.<BR><BR>

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