Math Magic : The life and times of a Math Magician

Here's how it works!

Pick a volunteer, have that volunteer write a number on the board(or paper). I change the size of the number depending on the volunteer. I usually have my 7th graders, start with a 5 digit number and tell them it needs to be larger than 10000(if I didn't they might pick 00000). After that I have them perform a series of computations that I make up as we go. For example, add their address, multiply times the number of siblings they have, ANYTHING I WANT! I ask how many steps they want me to make it, then do that many steps. The most important part of the trick is the final step. The final step has to be ONE of the following(these are the simplest, but there are others):
1) multiply by a multiple of 9 (9,18,27,36,...)
OR
2) take the final answer after all of your steps and rearrange them to form a second number, then subtract the small number from the big number.

After I have performed this final step I have the student put a star next to this final answer. Then I have them circle one number, not a 1 or a 0. After they have circled the number I ask them to call out the other numbers in the answer. While they call out the numbers I "cast out nines". Do this by adding the numbers together, when you have a total number, add the 2 digits. Subtract that number from 9 and that is the number they have circled. Here is an example with real numbers in only 3 steps.

35892
Add 1385
37277
Rearrange to become 72737
Subtract 72737 - 37277
35460
Circle 4
The other numbers are 3,5,6,0.
Added together = 14
1+4 = 5
9-5 = the circled # 4!!!