# How does this psychic puzzle thingey work?

I’ve seen puzzles of this type before but never remember how they’re constructed. Help!

http://mr-31238.mr.valuehost.co.uk/assets/Flash/psychic.swf

Due to clever mathematics, the answer is always 9, 13, 18, 27, 36, 43, 45, 54, 63, 72 or 81. In the chart, these 12 numbers always are associated with ONE symbol (but the symbol changes everytime you access the page).

Actually, the only possibilities are multiples of nine. But it is a clever trick.

But more important, how did you come across this puzzle? I ask because just today, I got an email from my dad with the very same link. He rarely emails me, and when I saw the OP I was almost sure it the same. ** straykat23**, are you my daddy? But seriously, I’m interested in knowing how this puzzle was propagated around the 'net. Any comments?

Someone sent this to me about a week ago… …after a couple times I checked and no matter which pair of numbers I picked it was always the same symbol. I also notice the symbol changed each time I accessed the page.
Very simple. But at first it seemed impossible.

Not 13!

In general, if you pick a two-digit number ab, then that number is really (10a+b). Then subtract (a+b), yielding 9a. So the number you end up with is always nine times the first digit of your original pick. Notice in the puzzle that all the multiples of 9 share the same symbol.