Hi candygal79,

DS questions test your ability to figure out if an answer is CONSISTENT or if it's INCONSISTENT. A consistent answer, no matter what it is, is SUFFICIENT.

In Fact 1, you deduced that X CANNOT ever be less than 0. THAT is CONSISTENT, thus Fact 1 is SUFFICIENT

In Fact 2, you deduced that since Y is positive and that X is 6 MORE than Y, then X CANNOT ever be less than 0. THAT is CONSISTENT also, so Fact 2 is SUFFICIENT.

The Final Answer is D; it's the answer you pick when each Fact is SUFFICIENT on its own.

GMAT assassins aren't born, they're made,
Rich

With data sufficiency question, the ONLY thing that matters is whether or not we can answer the target question with absolute certainty. The actual answer to the target question doesn't matter. It's all about whether we have sufficient information to be certain about our answer to the target question.

candygal79 wrote:If y > 0, is x less than 0?

1) xy = 16
2 ) x - y = 6

Target question: Is x less than 0?

REPHRASED target question: Is x negative?

Given: y > 0
In other words, y is POSITIVE

Statement 1: xy = 16
In other words, xy = POSITIVE value
Since we're told that y is POSITIVE, we get: x(POSITIVE) = POSITIVE value
From our rules about the products of positive and negative values, we can conclude, with certainty, that x is POSITIVE.
Is other words, x is definitely NOT negative
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: x - y = 6
We can rewrite this as: x = 6 + y
Since we're told that y is POSITIVE, we can write: x = 6 + (some POSITIVE value)
In other words, x will be greater than 6, which means we can conclude, with certainty, that x is POSITIVE.
Is other words, x is definitely NOT negative
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent