Do you need something to impress your friends or relatives? Then try this math trick that will convince everyone around you that you're a genius.
The world of mathematics is truly wonderful. Everything is ordered, everything is provable, everything is logical, everything makes perfect sense. It is a self-sufficient universe where everything fits together perfectly.
One of the indicators of this beauty is the existence of strange and unexpected patterns, for which it appears that they could be learned in elementary school, but in all likelihood this was not the case. And there is a trick that will easily convince people around you that you are a genius.
It's a very simple trick that really helps when multiplying above 9 x 11. So if you want to multiply, for example 25 x 11, you add the first two digits and place the sum between those first two digits.
So:
24 x 11 = 275, which is 2(2+5)5
36 x 11 = 396, which is 3(3+6)6
If the sum of these two digits is greater than 9, then you add 1 to the first digit.
So:
89 x 11 = 979, which is (8+1)79
What if you want to multiply a three-digit number by 11? It won't be a problem for a genius like you. This time between the first and third digits, you enter 2 numbers that are formed when you add the first two digits and when you add the second and third digits.
So:
253 x 11 = 2783 which is 2(2+5)(5+3)3
118 x 11 = 1298 which is 1(1+1)(1+8)8
If the sum of the first and second digits is greater than 9, add 1 to the first digit.
So:
754 x 11 = 8294 which is (7+1)2(5+4)4
But if the sum of the second and third digits is greater than 9, add 1 to the first sum or the sum of the first and second digits.
So:
357 x 11 = 3927 which is 3(3+5+1)27
But if the sums in both cases are more than 9, then you have to do both.
So:
789 x 11 = 8679 which is (7+1)(5+1)79
What if you want to multiply by 111? Pretty much the same, except now the middle numbers of the sum will be repeated.
62 x 111 = 6882 which is 6(6+2)(6+2)2
51 + 111 = 5661 which is 5(5+1)(5+1)1
If the sum is more than 9, things get a bit complicated. Namely, you have to add 1 to the second digit.
So:
79 x 111 = 8769 which is (7+1)(6+1)69
Who says math isn't fun?
