Question: Is x Less than 0?

Comment on Is x Less than 0?

I'm confused about this one. I found they're both sufficient. For either one, I wasn't including 0 as a possibility since the target question is asking if X is less than 0. Why in the 2nd part you're seeing if 0 can be a possibility?

I didn't solve for x for the 2nd one but I quickly found that any negative integer replacing X would make it less that -4.

gmat-admin's picture

Hi Gabriel,

For statement 1, we can see that x = 0 does not satisfy the inequality 2x > 3x.
So, there's no reason to include 0 in your analysis.

For statement 2, it isn't enough to just test negative values of x.

For example, let's try a different statement 2:
(2) x + 1 < 100
If we test a bunch of negative integers they will all satisfy the inequality x + 1 < 100.
However, this does not mean that x MUST be negative.
For example, if we test x = 25 also satisfies the inequality x + 1 < 100.

----Okay, back to the question at hand---------
When we solve the inequality for x, we get: x < 1/2

This is when it's crucial to remind ourselves of the target question: Is x < 0?
This is a YES/NO question.

So, if x < 1/2, then it's possible that x = -5, in which case the answer to the target question is "YES, x IS less than 0"

It's also possible that x = 0, in which case the answer to the target question is "NO, x is NOT less than 0"

Once we have two contradictory answers to the target question, we know that the statement is not sufficient.

Does that help?


Somewhat better. Need to practice more of these data sufficiency problems.

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