This post is made to learn “How to multiply, in your head, any two-digit number by eleven?” 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:
352
Now you
try:
53 x 11
Since 5 + 3
= 8, your answer is simply
583
One more.
Without looking at the answer or writing anything down, what is
81 x 11?
Did you
get 891? Congratulations!
85 x 11
Although 8
+ 5 = 13, the answer is NOT 8135!
As before,
the 3 goes in between the numbers, but the 1 needs to be added to the 8 to get
the correct answer:
935
Think of
the problem this way:
1
835
935
Since 5 + 7
= 12, the answer is:
1
527
627
Okay, now it’s your turn. As fast as you can, what is
a.) 83 x 11? b.) 78 x 11? c.) 28 x 11? d.) 63 x 11?
If you got
the answer 913,858, 308, 693 respectively then give yourself a pat on the back.
You are on your way to become a mathemagician.
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