Heh. Not too hard to work out. There are only a certain series of numbers that can possibly be the result of that process (all multiples of 9, I think). Each of those gets the same symbol every time in the chart, which is the symbol that comes up in the crystal ball. But it throws you off the scent because each time you click "try again", it juggles the symbols in the chart, so although all the possible correct answers still have the same symbol to each other, it is a different symbol than previously.

Do I win a prize?

Mork, your prize is enthusiastic praise and admiration.

Its pretty cool. Thanks Michael.

Didn't work everytime, but it did work pretty often.

I'll analyze after I've had my caffiene thank you....

Joe

First two tries surprised me. Then I got it. Not too bad.

Holy glavin! I'm agreeing with Mork! (Of course it's difficult to politicize mathmatics. Except for statistics...)

An easier way to see the trick is to try it with, say, 10. together = 1; 10-1 = 9. Then the next one, 11. 1+1= 2; 11-2 = 9. 12, 13 ... 20; 20-2 = 18...

I'm so LATE (Mork wins! wins! where's Mindy?)
I do like examples.

Ya know, the fact that it doesn't work everytime kinda makes it look better.

Try it with 58 [58 - 13 = 45]. won't work....

Ummm, 45 is a multiple of 9. 5*9=45

z = (10x + y) - (x + y)
z = 10x + y - x - y
z = 10x - x
z = 9x

The answer is always 9 times whatever the first digit of your number is.

Can't we work Orwell into this comment thread somehow?

My thoughts were the same as Mork's. he second time I did it I checked to see if 81 and 36 (my first two results) had the same symbol, and they didn't. That threw me off. Very clever.

Here's another tricky one.

If you want to have fun with showing someone else this site, have them open the page, read the instructions, then turn with them for a moment to look at the symbols... see that all the multiples of nine have the same symbol... then look away. With your back to them, tell them to silently pick their number, do the math, and click... When you hear the click tell them which symbol is about to appear. Adds to the laugh value.

dorkafork: please, please tell me how the heck they do that. I am stymied.

Dork: never mind. Got it. Very subtle.

Well, Mork got it so I guess I won't be revealing the secret. Congratulations, Mork. I'd give you a cookie for a prize, but you're far away.

Subtle...but still a cheap trick.

This is a neat trick, and I figured it out over a year ago, but I'm too lazy to try to re-figure it out.

Well the first two numbers I chose, the algorithm didn't work. Didn't have time for more than that.

The one with the cards is even easier. None of the initial five cards are shown when 'your' card is supposedly removed....

He he...

See what happens when I post before having my morning coffee?

Earlier I said that 58 didn't work....I was looking at the symbol at the wrong side....

yup....multiples of nine...seen the card trick before.

"Here's another tricky one."

The card trick one is pretty easy to figure out. You're shown two possible suits from each of the king, queen and jack. When the screen changes, none of the original cards are there because the suits have all been changed to the two that weren't shown on the original cards - if the king of diamonds and spades were there originally, they will show up as the king of hearts and clubs, etc.. Makes it harder to figure out because you can't go back to check, but just write down the suit of each card before you start and you'll see how the trick is done.