PRACTICAL GUIDE TO MENTAL MATH IN THE AGE OF SMART DEVICES

There is an expression “can’t see the forest for the trees”. It means an excess of detail interferes with your ability to understand something. If you research “mental math” or “doing math in your head” you will encounter the trees and not see the forest. You will find a myriad of tricks, written by math experts whose passion for the science is admirable but whose thoroughness you are likely to find too burdensome.

This guide has only five principles. You will not get lost. You will understand and implement the principles in this guide in about an hour and acquire an invaluable skill you’ll use every day of your life - even in an age when a smart device is in your pocket, on your desk, or even on your wrist.

The five principles are:

1Precision is not the point
2Two digits is enough
3Round before you multiply
4Take baby steps
5Turn around to subtract or divide