Hi ziyuenlau,

This prompt is based on a couple of Number Property rules - and you can TEST VALUES to solve it.

We're told that X and Y are POSITIVE. We're asked if X is less than Y. This is a YES/NO question.

1) √X < √Y

Since we know that X and Y are both POSITIVE, squaring or square-rooting those values will NOT change the "order" of them. Even if you're dealing with positive fractions, the 'order' will not change.

For example:
√X = 1/4 and √Y = 1/2
X = 1/2 and Y = about .71

Thus, the answer to the question is ALWAYS YES.
Fact 1 is SUFFICIENT

2) (X-3)^2 < (Y-3)^2

While X and Y are both POSITIVE, we could end up with an (X-3) or (Y-3) that is negative though... and that will impact the answer to the question.

IF... X = 2, Y = 10.... then (-1)^2 is less than (7)^2 and the answer to the question is YES
IF... X = 2, Y = 1.... then (-1)^2 is less than (-2)^2 and the answer to the question is NO
Fact 2 is INSUFFICIENT

Final Answer: A

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