BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

numbers

Expert replies
Source: — Problem Solving |

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.
Anju Agarwal
Quant Expert, Gurome

Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.

§ GMAT with Gurome § Admissions with Gurome § Career Advising with Gurome §
Join the discussion

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
Join the discussion

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
Join the discussion

by vipulgoyal » Mon Apr 22, 2013 2:23 am
Anju, please suggest am i missing something
Join the discussion

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.
Anju Agarwal
Quant Expert, Gurome

Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.

§ GMAT with Gurome § Admissions with Gurome § Career Advising with Gurome §
Join the discussion

by vipulgoyal » Mon Apr 22, 2013 2:40 am
Thanks, As always very well explained
Join the discussion