Practice GMAT Data Sufficiency Question
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If X is a positive integer, is X a prime number?
 X is an even number
 1 < X < 4
Correct Answer: B

Evaluate Statement (1) alone.
 Make a list of even numbers and evaluate whether they are prime:
2: Prime
4: Not Prime
6: Not Prime
8: Not Prime
10: Not Prime  Every single even number except 2 is not a prime number. However, since Statement (1) enables X to be prime (e.g., 2) and not prime (e.g., 4, 6, 8, 10, …), Statement (1) is NOT SUFFICIENT.
 Statement (1) alone is NOT SUFFICIENT.
 Make a list of even numbers and evaluate whether they are prime:

Evaluate Statement (2) alone.
 List the possible values of X, remembering that X is a positive integer such that 1 < X < 4:
X = 2: Prime Number
X = 3: Prime Number
Since all possible values of X given the parameters in Statement (2) are prime, Statement (2) is SUFFICIENT.  Statement (2) alone is SUFFICIENT.
 List the possible values of X, remembering that X is a positive integer such that 1 < X < 4:
 Since Statement (1) alone is NOT SUFFICIENT and Statement (2) alone is SUFFICIENT, answer B is correct.
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