Hi here was a question from one of my practice books:
If x and y are prime numbers, is y(x-3) odd?
1.) x>10
2.) y<3
The answer is D.
I understand how to get the answer but my question is the book's method. The book states that for any non value ds question such as the one above, the question can also be solved by disproving the choices. So in order for y(x-3) to be odd both y and (x-3) have to be odd. In the choices it is proven that neither can be simultaneously odd.
Is this a correct method? I was not sure if this was an accurate strategy to use because it seems from practice that it is more likely that the question requires the proof rather than disproof. If someone could please clarify that would be awesome thanks.
If x and y are prime numbers, is y(x-3) odd?
1.) x>10
2.) y<3
The answer is D.
I understand how to get the answer but my question is the book's method. The book states that for any non value ds question such as the one above, the question can also be solved by disproving the choices. So in order for y(x-3) to be odd both y and (x-3) have to be odd. In the choices it is proven that neither can be simultaneously odd.
Is this a correct method? I was not sure if this was an accurate strategy to use because it seems from practice that it is more likely that the question requires the proof rather than disproof. If someone could please clarify that would be awesome thanks.
