It’s very easy once you know the secret.
Consider the problem: 32 x 11
To solve this problem,
simply add the digits, 3 + 2 = 5,
put the 5 between the 3 and the 2, and there is your answer:
What could be easier? Now you try:Now before you get too excited, I have shown you only half
53 x 11
Since 5 + 3 = 8, your answer is simply
One more. Without looking at the answer or writing anything
down, what is
81 x 11?
Did you get 891?
of what you need to know.
Suppose the problem is 85 x 11
Although 8 + 5 = 13, the answer is NOT 8135 !
See how to resolve this
Here is another example. Try 57 x 11.
57 x 11 see the answer
Okay, now it’s your turn. As fast as you can, what is 77 x 11?
If you got the answer 847, then give yourself a pat on the
back. (LoL) You are on your way to becoming a mathematician.
Now, I know from experience that if you tell a friend or
teacher that you can multiply, in your head, any two-digit number
by eleven, it won’t be long before they ask you to do 99 x 11.
See the answer
Okay, take a moment to practice your new skill a few times,
then start showing off. You will be amazed at the reaction you
get. (Whether or not you decide to reveal the secret is up to you!)
Can we use this method for multiplying three-digit numbers
(or larger) by eleven?
Absolutely. For instance, take the problem 314 x 11,
How to resolve this ?
But we’ll save larger problems
like this for later.
More practically, you are probably saying to yourself,