Fun with number 11
Now we try the tricks which can make calculation by 11 easy. We will also learn how to multiply by 22, 33, 44, 55, 66, etc. As it is nothing but 11 x 2, 11 x 3, 11 x 4, 11 x 5, 11 x 6 respectively.
Steps involved:
To multiply a number by 11 put a 0 in the beginning and at the end of the number. Starting from the digit’s place add two consecutive digit. Remember to go from right to left.
Examples
342 x 11 = 03420 = 0+3 /4 + 3/2 + 4/0 + 2 = 3762
Explanation: We added 0 at the end and the beginning of 342 and got 03420. Now, as you see we broke the number by taking each consecutive number and added them. The first part is 0 + 2 = 2, the first number of our answer, then we took 2+4 and got 6, second number of our answer and so on.
4932 x 11 = 049320 = 0 + 4/4 + 9/3 +9/3 + 2/0+2 = 54252
Explanation: In this case when we add 3 + 9 we write down 2 and carry forward 1, we again get 4 + 9 + 1 we write down 4 and carry forward 1. We add 4 + 1 and get 5
In the above case if we need to multiply by 22. Then we first multiply by 2 and then by 11.
312 x 22 = 624 (312 x2) x 11 = 06240 = 0 +6/6 + 2/4 + 2/0 + 4 = 6864
Explanation: Here we are trying to multiply with 22. Hence we first multiply the main number with 312 with 2 and get 312 x 2 = 624. And then multiply the same number with 22. Rest of the steps remain the same.
312 x 22 = 03120 x 11 x 2 = (0+3 / 3 + 1 /2 + 1 /0 + 2) x 2 = 3432 x 2 = 6864
Explanation: This is the exact same sum as above. In this case you multiply the end answer by 2 and get the exact same answer.
Similarly we can calculate any number into any multiple of 11. Even 11 x 11. We just repeat the process twice.
