clearly, since 9 is divisible by 9, but not by 6, it is not sufficient.
On the other hand, 12 is not divisible by 9, but is divisible by 6, so it is not necessary.
Let n be a natural number. If n is divisible by 9, that is neither a necessary nor sufficient condition for n being divisible by 6, right? Because I'm not sure about the wording of the question asking whether it is either necessary or sufficient, but I believe it is neither.
For example:
6*5 = 30
So 30 is divisible by 6, but is not divisible by 9.
Therefore, n being divisible by 9 is neither a necessary nor sufficient condition for n being divisible by 6.
1 answer
1 answer