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Q is less than 10. Is Q a prime number?

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Source: — Data Sufficiency |

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by [email protected] » Mon Nov 27, 2017 5:55 pm
Hi ardz24,

We're told that Q is less than 10. We're asked if Q is a PRIME number. This is a YES/NO question.

1) Q^2 - 2 = P; P is prime and P < 10.

The information in Fact 1 severely limits the possible values of P (which will limit the possible values of Q. Since P is PRIME and P < 10....
P can be 2, 3, 5 or 7
By extension, Q could be +2, - 2, +√5, -√5, +√7, -√7, +3 or -3
IF...
Q=2 or 3, then the answer to the question is YES.
Q = any of the other values, then the answer to the question is NO.
Fact 1 is INSUFFICIENT

2) Q + 2 is NOT prime, but Q is a positive integer.

The information in Fact 2 limits the possible values of Q to the following: 2, 4, 6, 7 or 8
IF...
Q = 2 or 7, then the answer to the question is YES.
Q = 4, 6 or 8, then the answer to the question is NO.
Fact 2 is INSUFFICIENT

Combined, there's ONLY ONE value that 'fits' both Facts (Q=2)
Combined, SUFFICIENT

Final Answer: C

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