I can’t figure out how this thing works but it does.
Have fun! 
-Paul
For whatever reason, the equation always yields a multiple of nine. The webpage is set up so that every multiple of nine has the same symbol. The symbols are shuffled each time you click on the ball, but every multiple of nine gets the same, new symbol.
I’m certainly glad you said that Jerry. Otherwise I’d have gone nuts.
Steve
I was afraid I’d get in trouble for spilling the beans.
I knew if I followed the instructions, it would show whatever answer I had picked, so I clicked on the ball without doing any math. I did that a few times and saw that it gave a different symbol each time.
Then I did the math and got a number. I looked at the symbol for that number. Then I used their example and got another number. I looked at that number and saw it had the same symbol as the number I tried first.
I noticed that both were multiples of nine, so I looked at all the multiples of nine and saw that they all had the same symbol. Then I clicked on the ball and saw that all the multiples on nine had the same symbol again, but it was a new symbol. I did that a few times, and it kept doing the same thing, so I figured I was done.
Here’s why. Note that a two digit number, such as 36, means (in base 10 arithmetic), 3x10 + 6.
Okay, here we go. A two digit number has the form 10a + b, where a and b are single digit numbers, 1<=a<=9, 0<=b<=9. The sum of the digits is a+b. Subtracting the sum from the original number, we get
(10a+b)-(a+b) = 10a+b-a-b = 9a
Thus the result is always a multiple of 9.
Jerry, I was actually going nuts trying to figure it out. I knew it had to be something in the numbers.
How does this one work?
All the cards are changed. Any care that you choose would be missing. The think is you focus on the one you choose and don’t really notice the alternatives.
Steve