How in the hell does this work?

[hogleg]

I could have circled any number??

http://digicc.com/fido/

Arg

[PKM]

my wife's a hs math teacher, she does this sh*t all the time on her kids to amaze them, i'll get her to look at it and figure it out. saddly the answer will be some retarded math aligorum or therum or whatever.

[tltrude]

Try adding the final "uncircled" digits together and subtract the result from 18. The answer will give you the circled number.

Hint - When you add all of the digits in the final number, it always equals 18.

4321
-1234
-------
30(8)7 = 18
073 = 10

18 - 10 = 8

It is simple Algebra.

[Jack Ruby]

Maths is really the thing im weakest at, numbers just dont make sense to me.

Did you ever see that Lord Vader 20 questions site, you can beat him but he is pretty clever:

http://www.sithsense.com/flash.htm

[hogleg]

It is simple Algebra.

the only algebra I can remember is Boolean Algebra and thats fading fast

[tltrude]

Nice one Jack. Try this one....

http://www.superlaugh.net/1/flashmindreader.htm

[Jack Ruby]

I saw that one a couple years back Tom, my friend worked it out, we have been calling him Rain Man ever since