I found http://www.metacafe.com/watch/315070/cool_math_trick_really_fast_multiplication/" video tutorial about a week ago and got hooked on the method. It's really simple once you get into it and works wonders. It can be easily extended to bigger numbers as well. I can't understand why they don't teach this at school. Now, do you know any other fast calculation methods? I want to learn them all and become as calculator-independent as possible(yeah, I know).