Question

Show that a number n is divisible by 3 if and only if the sum of its digits are divisible by 3.

Answer 1

For example

n=9471

Then,sum all the digits in the number

9+4+7+1=21

And 21 is divisible by 3 which is 7.

So this was a example.

Do in the same way for other numbers to know the divisibility test of a number by 3.