Divisibility by 11

Difference between sum of odd and even position digits divisible by 11.
Example:

4+2=6,6−6=0 ⇒462 divisible by 11

Note: Always work.

$n≡(sum ofodd-positiondigits-sumofeven-positiondigits)(mod11)$

$Check\; 2728:$

• $Odd\; Positions$→ 8 + 7 = 158 + 7 = 15
• $Even\; Positions$→ 2 + 2 = 4
• $Difference:\; 15\; -\; 4\; =\; 11\; (mod\; 11)$

So 2728 is divisible by 11.