



Copyright © Vic Evans, 1996-2013, ALL RIGHTS RESERVED

I will assume that you know your multiplication table reasonably well up to 10x10.

Try this:



Take 15 x 13 for an example.

Always place the larger number of the two on top in your mind.

Then draw the shape of Africa mentally so it covers the 15 and the 3 from the 13 below. Those covered numbers are all you need.

First add 15 + 3 = 18

Add a zero behind it (multiply by 10) to get 180.

Multiply the covered lower 3 x the single digit above it the "5" (3x5= 15)

Add 180 + 15 = 195.

Want to Learn More? The one book I recommend



May be out of print



"Super Math-E-Magics"

by V.A. Stephen Lenaghan

It may be available from Amazon.com or one of the other online sellers of used books

To multiply any two digit number by 11:

For this example we will use 54.

Separate the two digits in you mind (5__4).

Notice the hole between them!

Add the 5 and the 4 together (5+4=9)

Put the resulting 9 in the hole 594. That's it! 11 x 54=594

The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the "ones" digit in the hole and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 ... 11 x 57 = 627

Practice it on paper first!

Take the "tens" part of the number (the 2 and add 1)=3

Multiply the original "tens" part of the number by the new number (2x3)

Take the result (2x3=6) and put 25 behind it. Result the answer 625.

Try a few more 75 squared ... = 7x8=56 ... put 25 behind it is 5625.

55 squared = 5x6=30 ... put 25 behind it ... is 3025. Another easy one! Practice it on paper first!

Look for the nearest 10 boundary

In this case up 3 from 37 to 40.

Since you went UP 3 to 40 go DOWN 3 from 37 to 34.

Now mentally multiply 34x40

The way I do it is 34x10=340;

Double it mentally to 680

Double it again mentally to 1360

This 1360 is the FIRST interim answer.

37 is "3" away from the 10 boundary 40.

Square this "3" distance from 10 boundary.

3x3=9 which is the SECOND interim answer.

Add the two interim answers to get the final answer.

Answer: 1360 + 9 = 1369

Thanks To Ryan

Take for example the number 51236 X 11.

First, write down the number with a zero in front of it. 051236 The zero is necessary so that the rules are simpler.

Draw a line under the number.

Bear with me on this one. It is simple if you work through it slowly. To do this, all you have to do this is "Add the neighbor". Look at the 6 in the "units" position of the number. Since there is no number to the right of it, you can't add to its "neighbor" so just write down 6 below the 6 in the units col.

For the "tens" place, add the 3 to the its "neighbor" (the 6). Write the answer: 9 below the 3.

For the "hundreds" place, add the 2 to the its "neighbor" (the 3). Write the answer: 5 below the 2.

For the "thousands" place, add the 1 to the its "neighbor" (the 2). Write the answer: 3 below the 1.

For the "ten-thousands" place, add the 5 to the its "neighbor" (the 1). Write the answer: 6 below the 5.

For the "hundred-thousands" place, add the 0 to the its "neighbor" (the 5). Write the answer: 5 below the 0.

That's it ... 11 X 051236 = 563596