Question

Test the divisibility of the following numbers by $7$.

$10311$

Answer 1

A number is divisible by $7$ if the difference between twice the last digit and number formed by other digits is either $0$ or a multiple of $7$

In the given number $10311$ last digit is $1$. Twice of $1$ is $2$ and the number formed by other digit is $1031$.

Diffierence$=$$1031-2=1029$, which is divisible by $7$.

Hence, the number $10311$ will be divisible by $7$.