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Lets take any two digit number and multiply it with 11. It probably takes more than 15 seconds to find the answer right? Well here is a
trick which lets you find product of any two digit number with eleven in less than 5 seconds.
Take a number suppose 34. Now the
first and second
digits which are '3' and '4'
will also be first and last digit of the product with eleven:- 3_4
Now the middle number will be the
sum of
those two digits
. In this case it is 3+4=7.
So join the digits and the answer will be 374!.
Now an obvious question occurs to our minds that "What if the sum of the two digits is more than 10?". Well you just apply the same algorithm but beacuse sum is more than 10, the one gets carried and adds to the first digit.