mental math

3 tips by hand 'like hacking' worth sending to the future
Do not know when to appear, but people have created a lot of recipes, tips to show the usefulness until today (and maybe forever after).
How to calculate 2 digits of Japanese people: Just know how to count
This will be the mental math method
Tips 'mental arithmetic' you can't find in textbooks
Learn fast calculation methods, mathematical rules that you can't find in textbooks or in school chairs ...
The world 'living computer' dies
Shakuntala Devi, Indian math genius, was named