This is a little trick I learned while listening to Art Bell
Turn any number into a 9:
Lets take say any random number....
how about
158:
ok
so 1+5+8 = 14
158-14 = 144
1+4+4 = 9
lets try a little bit of a larger number....
984:
9+8+4 = 21
984-21 = 963
9+6+3 = 18
1+8 = 9
Two digit number?
61:
6+1 = 7
61-7 = 54
5+4 = 9
Four Digits?
4568:
4+5+6+8 = 23
4568-23 = 4545
4+5+4+5 = 18
1+8 = 9
As far as I can tell this works with any number.