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Q a prime

by sanju09 » Tue Feb 08, 2011 12:05 am
Q is less than 10. Is Q a prime number?

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

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


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by gmatmachoman » Tue Feb 08, 2011 12:11 am
Q is less than 10. Is Q a prime number?

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

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

Pick C

st 1 :
Q can be V7, still P can be 5 or Q can be 2 and P can be 2. Insufficient.

st 2 :
Q can be 4 or 6.

Combining we have Q = 2, and P =2.

Pick C
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by Anurag@Gurome » Tue Feb 08, 2011 1:49 am
sanju09 wrote:Q is less than 10. Is Q a prime number?

[1] Q² - 2 = P; P is prime and P < 10.
[2] Q + 2 is NOT prime, but Q is a positive integer.
Statement 1: Possible values of P are 2, 3, 5, and 7.
Hence, possible values of Q² are 4, 5, 7, and 9.
For some of the above Q is prime (Q = 2 or 3) and for some not (Q = -2 or -3 or √5 etc)

Not sufficient

Statement 2: (Q + 2) is not prime and Q is an integer such that 0 < Q < 10.
Possible values of Q are 2, 4, 6, 7, and 8.
For some of the above Q is prime (Q = 2 or 7) and for some not (Q = 4 or 6)

Not sufficient

1 & 2 Together: Only possible value of Q is 2, which is prime.

Sufficient

The correct answer is C.
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