Okay, this one is probably going to get laughed out of town, but it's annoying me so I shall ask it anyway. 1. Take any number of 2 digits or greater, reverse it (i.e. 12 becomes 21 or 4765 becomes 5674). 2. Take the 'reversed' number away from the original number. 3. Why is the answer to this simple sum ALWAYS either 0* or divisible by 3? Try it with any random numbers 12-21 = -9 4765-5674 = -909 863789532 - 235987368 = 627802164 All of these answers are divisible by 3. WHY? * I had to put in the bit about it could be 0 for those who will point out that 121 or anything similar when reversed is still 121 and hence taken away from itself results in 0.