Speed Mathematics: Secrets of Lightning Mental Calculation

I've always been fascinated by savants who have the ability to perform amazingly complex math calculations mentally. Over the years I've examined systems from Vedic Maths to the methods of Trachtenberg in a bid to improve my ability to perform mental calculations. Some years ago I came across a book called "Speed Mathematics - Secrets of Lightning Mental Calculation" by the Australian author Bill Handley. This book is an accessible manual of techniques for performing rapid mental calculations. An example of the type of calculation explained in this book is the author's method of multiplication.This method uses a reference number to make multiplication easier. In the example below the reference number used is 100.


In this example we want to multiply 98 x 115.

Step 1 - 98 is 2 less than the reference number so we mentally note -2.
Step 2 - 115 is 15 more than the reference number so we mentally note +15.
If you were writing this on paper it could be represented as follows:

Step 3 - Add or subtract diagonally. eg 98 + 15 or 115 -2. The answer is the same - 113
Step 4 - Multiply the result of the last step (113) by the reference number (100) eg 113 x 100 = 11300
Step 5 - Multiply 2 x 15 = 30 but because one of the numbers is negative the answer is negative. ie -30
Step 6 - Subtract the result of the last step from the result of Step 4. ie 11300 - 30 = 11270

So 98 x 115 = 11270. This method when done in the mind takes only a couple of seconds to complete.

The methods in this book are both simple and effective. With a little practice you will definitely be able to make use of these techniques to perform your own rapid mental calculations. This is a book that I would highly recommend to anybody who is sick of relying on electronic calculators to solve their daily math problems.