Tricky Data Sufficiency Answer Choice

[Raj]

Hi,

I understand GMAT Focus questions CANNOT be posted here, so I am just going to keep this question a bit abstract, but I still hope to make my point:

While using the 2 statements A and B in a question,
if from A, you narrow down to values of X to be 0, 2
from B, you narrow down to values of X to be 0, 3

What answer should one choose and why?

From the explanation given, they argue that since both statements are true (answer C), the only way they can be true is if X = 0. I think I agree with that explanation but still not convinced 100%.. would like to see your perspective on this.

Thanks,
-Raj.

[RA]

The 2 DS statements don't contradict each other and are always true/valid.

If x =2 or 3 then one of the statements would not be true/valid. Only x=0 validates both the statements and is therefore the solution.

Hope that helps.

[esledge]

You also need to consider the nature of the question: Value vs. Yes/No.

Let's use your statements:
(1) x = 0 or 2
(2) x = 0 or 3

For a value question such as "What is the value of x?" neither of those statements give a single answer, so we must combine the statements. When combining statements, the only valid values are those on BOTH lists: (1) & (2) combined tell us that x = 0. Note that x can't be 2, as that disagrees with statement (2). Likewise, x can't be 3, as that disagrees with statement (1). The answer to this question is C.

For a Yes/No question such as "Is x >= 0?" you wouldn't even need to combine the statements.
(1): Both 0 and 2 are >=0, so the answer is a definite yes. Sufficient.
(2): Both 0 and 3 are >=0, so the answer is a definite yes. Sufficient.
The answer to this question is D.

For a Yes/No question such as "Is x = 0?" you would have to combine the statements.
(1): x may be 0 (Yes) or may be 2 (No). Insufficient.
(2): x may be 0 (Yes) or may be 3 (No). Insufficient.
(1) & (2): x must be 0 (as discussed above), therefore the answer is a definite yes. Sufficient.
The answer to this question is C.