OK, I figured it out. Cute.

Let the first digit of your number be x, and the second digit y.

Then after you do the computation you will get 10x+y-x-y=9x.

The applet puts the same symbol next to all the multiples of 9 so you are assured of picking it.

Good for you! So did I. Let’s not tell anyone.

Nerdy Nitpick: It’s Flash, not Java.

An easy way to tell? It’s called the Flash Mind Reader.

That’s cool. Once again it shows you not to assume anything.

Sorry to be such a chowderhead, but can someone explain it to me, reeeaal sloooowwww like. I’m not the swifted gazelle on the plain when it comes to that there numberology stuff.

Start with a two digit number AB. That 10 times A, plus B. Take A + B away from it, and you get 9 times A. The only possible answers are the numbers from 9 times 1, through to 9 times 9, i.e. 9, 18, 27, …, 81. These all have the same symbol next to them,

Yes, the answer will always be a multiple of 9. The game encourages you to try it again. So you try another 2-digit number. It has a different symbol next to it than the last number you tried. And it figures out your symbol again!! The trick is, all the symbols beside powers of 9 are the same, and it puts a different symbol next to the powers of 9 each time you try the game! That’s what makes it seem like it’s reading your mind.