11 * 22 In A Flash (Smart Multiplication)

  Two days ago, I had a mathematical epiphany. Sitting in my car, waiting for the traffic to move, I started practicing multiplication exercises mentally. Quite by coincidence, I stumbled on a simple trick for multiplying any number by 11.

11 * 22 = 242
Separate the two digits and insert the sum of the the two digits in between

2 (2+2=4) 2

11 * 512 = 5632
5 (5+1) (1+2) 2

11 * 8961 = 98571
Same prinicple, separate the two digits on either end, add sums from the middle with adjacent digits:
8 (9+8) (9+6) (6+1) 1 = (From the left, usual addition rules) 98571

  Resist the urge to use a calculator. Pretty sure everyone else learns multiplication table tricks at school. I missed out. It would have made Math class in primary school so much more enjoyable.