Question

For any positive integer n, show that one and only one out of n, n+3, n+6 or n+9 is divisible by 4.

Answer 1

Using Euclid division lemma
N=1,=1,4,7,10 4 is disible by 4 same as this
N=2.......
N=3......
This shows 1 no among 4 divisible by 4