Brain Exercise Using Mental Maths - Introduction

This is my first attempt at writing a blog.  This blog will be about exercising our brain using mental maths.  It is going to be fun as well as good for your brain.  Just for a teaser, you will be able to multiply a two digit number by 99 instantaneously.  I taught the method to a group of 12 year old students and within less than 10 minutes they mastered the method.  Eventually this brain exercise will lead you to discover new methods yourselves.  Let's first see the response to this blog....