Question

How to test divisibility of 11

Answer 1

Take the alternating sum of the digits in the number, read from left to right. If that is divisible by 11, so is the original number.

For example, Take 1375.

1 – 3 + 7 – 5 = 8 - 8 = 0 which is divisible by 11. Therefore, 1375 is divisible by 11.

Take another example 998250

9 - 9 + 8 - 2 + 5 - 0 = 22 - 11 = 11 which is divisible by 11. therefore, 998250 is divisible by 11.

Let us take another example 56763

5 - 6 + 7 - 6 + 3  =  15 - 12  = 3 which is not divisible by 11. therefore, 56763 is not divisible by 11.

Answer 2

example = original number is 2728 has alternating sums of digits 2-7+2-8=-11 that is divisible by 11 so 2728is divisible by 11