Multiply two-digits numbers by 11 shortcut

53 x 11
Write 3 as the right most digit in 53
3
5 + 3 = 8. Write that to the left of 3
83
Then write the 5 as the left most digit
583

35 x 11
Write 5 as the right most digit in 35
5
3 + 5 = 8. Write that to the left of 5
85
Then write the 3 as the left most digit
385

57 x 11
Write the 7 in 57 as the leftmost digit
7

5 + 7 = 12
Write the 2 in 12 as the next digit
27

Since our last sum was 10 or greater, we add 1 to the 5 in 57 to get 6
627

91 x 11
Write the 1 in 91 as the leftmost digit
1

9 + 1 = 10
Write the 0 in 10 as the next digit
01

Since our last sum was 10 or greater, we add 1 to the 9 in 91 to get 10
1001