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by vipulgoyal » Mon Apr 22, 2013 1:41 am
6. Integer A and N, is A a prime number?
1) Besides 1, A is the least factor of N
2) A has two factors.
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by Anju@Gurome » Mon Apr 22, 2013 1:50 am
vipulgoyal wrote:6. Integer A and N, is A a prime number?
1) Besides 1, A is the least factor of N
2) A has two factors.
Statement 1: If A is the least factor of N, A must be a prime number as except 1 all the number are made of prime numbers.

Sufficient

Statement 2: Only prime numbers have two factors, 1 and the number itself.
So, A is a prime number.

Sufficient

The correct answer is D.
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by vipulgoyal » Mon Apr 22, 2013 1:55 am
positive no which have 2 factors 1 or itself called prime i guess, here nothin like +ve mentioned
thats was my concern
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by vipulgoyal » Mon Apr 22, 2013 2:04 am
-5 is not a prime no though it has 2 factors -1 and -5 , I believe thats what the tricky part in qustion, hence ans is A
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by vipulgoyal » Mon Apr 22, 2013 2:23 am
Anju, please suggest am i missing something
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by Anju@Gurome » Mon Apr 22, 2013 2:31 am
vipulgoyal wrote:-5 is not a prime no though it has 2 factors -1 and -5 , I believe thats what the tricky part in qustion, hence ans is A
GMAT never asks for negative factors.
You won't see this problem in GMAT simply because GMAT would've said 'Positive integers A and N..." or used the phrase 'positive factors'.

Apart from that, if we consider negative factors just for the sake of mathematical discussion, any negative integer x has at least 4 factors : 1, -1, x, and -x
Same is true for any positive integer.
In your case, -5 has four factors : 1, -1, 5, and -5

But for most of the practical purpose negative factors do not mean anything. So they have their implications only in mathematical discussion. And that's why GMAT doesn't ask for them.

Hope that helps.
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by vipulgoyal » Mon Apr 22, 2013 2:40 am
Thanks, As always very well explained
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