Fast Maths Trick - How to Multiply any two digit number with 11

 Multiplying a two digit number with eleven in your head is very easy once you know the trick.This is one of my favourite trick , ok let me share the secret with you know .
Lets begin by taking the example

consider 43 X 11


Here you simply have to add the digits of the 2 digit number which is to be multiplied by 11 that is (4+3)=7
now place this digit (7) in between 43 ,therefore the answer will be 4(7)3.

What could be easier? Now you try:
63 X 11
 your answer is simply
693

One more. Without looking at the answer or writing anything down, what is
81 X 11 ?
Is your answer  891?
Congratulations!

Now before you get too excited, I have shown you only half
of what you need to know. Suppose the problem is
85 X 11
the answer will not be 8(13)5 !!

now the sum of the digits is 13 which is a 2 digit number so the number that will be inserted in between will be 3  and the 1 will be added to 8. Therefore the answer will be 935.

You can think of it as

   805
+ 13
--------
   935


Lets take another example of this type

66 X 11

Sum is 12 which is a two digit number so the digit to be inserted will be 2 and 1 will be added to 6
the answer will 726



Now you know the secret .You can calculate faster than the calculator

Reference Guru