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by sanju09 » Thu Mar 19, 2009 3:28 am
Is x a prime number?

1. x is an even number.

2. x can not be divided evenly by an odd number other than 1.



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by scoobydooby » Thu Mar 19, 2009 3:37 am
x prime?

1) x=even, x can be 0, 2, 4, 6......
x is prime only if x=2. cant say if x is prime definitely


2) this statement means x=even in other words. just like statement 1.

combining doesnt add extra info
hence E
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by Stuart@KaplanGMAT » Thu Mar 19, 2009 3:46 pm
scoobydooby wrote:x prime?

1) x=even, x can be 0, 2, 4, 6......
x is prime only if x=2. cant say if x is prime definitely


2) this statement means x=even in other words. just like statement 1.

combining doesnt add extra info
hence E
Statement (2) doesn't mean "x = even". It means "x has no odd factors other than 1". For this to be true, x must be a power of 2.

For example, "6" has a factor of 3, so it doesn't fit statement (2).

However, even though your reasoning isn't perfect, your answer is correct.

From (2), x could be any power of 2, i.e. 2, 4, 8, 16, 32, ...; since it could be 2 (prime) or any other power of 2 (not prime), it's insufficient.

Since (2) gives us numbers that are all a subset of (1) (i.e. every number that fits (2) also fits (1)), combining doesn't help us at all: choose (E).
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by Ian Stewart » Thu Mar 19, 2009 4:12 pm
Just one exception to add to Stuart's excellent explanation - from Statement 2, x could also be equal to 1, so there is one number which satisfies Statement 2 but not Statement 1. That doesn't affect the answer in any way, however.
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