EXCLUSIVE DIVISION RULE FOR 7

Let me explain this rule by taking examples

If you had 343, you would double the last digit to get six, and subtract that from 34 to get 28.
If you get an answer divisible by 7 (including zero), then the original number is divisible by
seven. If you don't know the new number's divisibility, you can apply the rule again.

EXAMPLE.

Example -:
623: 62 - (3 × 2) = 56 = 7 × 8
483: 48 − (3 × 2) = 42 = 7 × 6