How to Multiply 11's, a Trick to doing Mental Math

I refer to any number under 10 as a basic fact number. The basic facts for 11 are realistically simple. 2 X 11 = 22 . It is simply the digit twice. This is a simple process but the trick comeswhen you get to 10.

Learning Tricks in math will amaze your teachers and friends as you become the human calculator. There are so many different tricks in multiplication but I always encourage that everyone learn and memorize those basic 10 by 10 facts.

Now it is time to multiply by 11.

We are going to multiply 11 by 13.

Place the 1 and the 3 at opposite ends of the problem with a space in the middle. In this space there is room for another digit

Now add 1 +3 for the middle digit

Your answer is 143

Try it with a different number

11 x 24

2 __ 4

2 (2+4) 4

264

Now let's try a real tricky one

11x 19

1 _ 9

1 (1+9) 9

now wait a minute 1 +9 is a two digit number. So we are going to take 10 and the zero will be the middle digit while we add the 1 to the hundreds digit.

SO (1+1) 0 9

209