Question

divisibility test of 7

Answer 1

To find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number. 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.

Answer 2

Answer:

if the difference between twice the last digit and number formed by other digit is either 0 or multiple of 7