Question

What is a counterexample of the following conjecture any number that is divisible by 3 is also divisible by 6

Answer 1

Any odd multiple of 3 would be the counterexample of the given conjecture.

That is 3(2n - 1), for any natural number n, will be divisible by 3 but not divisible by 6 as 2 is not a factor.

Examples:

3(3) = 9

3(5) = 15

3(7) = 21 are some examples.