Fun with Math

Take any number between 10 and 99. Go ahead...take it. Now, add the two digits together. For example, if your "randomly" selected number just happens to be 69, add 6 and 9. Now subtract the total, i.e. 15 from 69. You'll ALWAYS end up with a multiple of 9.

69 -> 6+9 = 15 -> 69-15 = 54

I think I just blew my own mind.