ykaiim wrote:

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.

Given:

q<10. Question:

q=prime?

(1)

q^2-2=p=prime<10 --> if

p=7, then

q=3=prime or

q=-3\neq{prime}. Not sufficient.

(2)

q+2\neq{prime},

q=positive \ integer. If

q=2 then answer is YES but if

q=4, then answer is NO. Not sufficient. From this statement

q can take the following values: 2, 4, 6, 7, 8 (remember

q<10 and

q+2\neq{prime}).

(1)+(2) The only value from (2) that satisfies

q^2-2=prime<10 is when

q=2=prime. Sufficient.

Answer: C.

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