Question

Select a counter-example that makes the conclusion false.

3 is prime, 5 is prime, 7 is prime

Conclusion: All odd numbers are prime.

Counterexample:

Answer 1

well 9 is also an odd number but it is not prime!!!

Answer 2

15, 21, 25, 27, and so on.....

Answer 3

Any number may be called "prime": it is entirely up to each person's subjective evaluation as to whether a number has been divided fairly.

Answer 4

mathmagician: Not if you assume the usual definition of "prime".

Since only a counter example is needed, 9 will do just fine: 9 = 3 x 3, so it has factors that are not 1 and the number itself, therefore it is not prime.