Hi jaspreetsra,
This DS question is an example of a Symbolism question. In Symbolism questions, you'll be given a "made up" math symbol to work with and a description of how the Symbol "works." You'll then be asked to perform a calculation using the symbol.
Here, we're told that [X] is the LEAST INTEGER that is GREATER THAN OR EQUAL to X. We're asked if [X] = 0? This is a YES/NO question.
Before we get into the 2 Facts, here are some examples of how this Symbol works:
[2] = 2 since 2 is the LEAST integer that is greater than or equal to 2.
[1/2] = 1
[-2.5] = -2
Fact 1: -1 < X < 1
Here, we can TEST VALUES.
IF....
X = 0, then [0] = 0 and the answer to the question is YES.
X = 1/2, then [1/2] = 1 and the answer to the question is NO.
Fact 1 is INSUFFICIENT
Fact 2: X < 0
IF...
X = -1, then [-1] = -1 and the answer to the question is NO.
X = -1/2, then [-1/2] = 0 and the answer to the question is YES.
Fact 2 is INSUFFICIENT
Combined, we know that...
-1 < X < 1
X < 0
So we have a range of.....
-1 < X < 0
This means that X is a NEGATIVE FRACTION. According to the Symbol, no matter what negative fraction we use for X, the LEAST INTEGER that is greater than or equal to X will be 0 EVERY TIME. Thus, the answer to the question is ALWAYS YES.
Combined, SUFFICIENT.
Final Answer: C
GMAT assassins aren't born, they're made,
Rich