How to know if a number is divisible by 7?

Let us explore the divisibility rule of 7.

Answer: The rule is that the last digit of the given number should be multiplied by 2 and then subtracted with the rest of the number leaving the last digit. If the difference is 0 or a multiple of 7, then it is divisible by 7. 

Let us understand the rule in detail:

Explanation:

Follow the loop:

1. Separate the last digit from the number.
2. Double the last digit.
3. Subtract that from the truncated number thus obtained.
4. Continue this process till you are left with only one digit.
5. If the single digit at the end is 0 or 7, then the original number is divisible by 7.

For example: 945     

94 - 2(5) = 94 - 10 = 84

8 - 2(4) = 8 - 8 = 0

So, 945 is divisible by 7.

Hence, the divisibility rule of 7 is to double the last digit and subtract from the remaining number and continue this until only one digit remains. If the end result is 0 or 7, then the original number is divisible by 7.