Question

What is the divisibility rule of $3$and $9$?

Answer 1

Divisibility rule of $3$and $9$.

Divisibility rule of $3$: If the sum of its digits is divisible by $3$then the number is completely divisible by $3$.

For example: $108$ the number is divisible by $3$as sum of its digits $1+0+8=9$ is divisible by $3$

Divisibility rule of $9$: If the sum of its digits is divisible by $9$ then the number is completely divisible by $9$.

For example: $504$ the number is completely divisible by $9$ as sum of its digits $5+0+4=9$ is divisible by $9$.

Thus, if the sum of its digits is divisible by $3$then the number is completely divisible by $3$and if the sum of its digits is divisible by $9$ then the number is completely divisible by $9$.