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prime

by tohellandback » Fri Jul 03, 2009 1:58 am
If n is an odd integer greater than 1, is n prime?
1) n is a factor of 56
2)14 is a factor of 2n
The powers of two are bloody impolite!!
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Source: — Data Sufficiency |
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by Robinmrtha » Fri Jul 03, 2009 3:24 am
Statement 1:
n is a factor of 56
the factor of 56 are 2 x 2 x 2 x 7
the only odd factor is 7 which is odd...
therefore A is sufficient

Statement 2:
14 is a factor of 2n
i.e 2n/14 = k ( an integer)
or n/7 = k
or n= 7k
so n is a multiple of 7 and not necessarily a prime....
only when k =1, it is prime...
when k= 2, it is not prime...
so, statement two give multiple values of k which may or may not be prime...
hence its insufficient

So, the answer is A...
OA please?
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by tohellandback » Fri Jul 03, 2009 3:36 am
OA is A
The powers of two are bloody impolite!!
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by benissleeping » Fri Jul 03, 2009 4:57 am
the only thing i would add to statement 2 below:

is that k=2 is not an option as n had to be odd.

However say k=9 then n would be odd and not a prime.

Still the result is the same A.
Robinmrtha wrote:Statement 1:
n is a factor of 56
the factor of 56 are 2 x 2 x 2 x 7
the only odd factor is 7 which is odd...
therefore A is sufficient

Statement 2:
14 is a factor of 2n
i.e 2n/14 = k ( an integer)
or n/7 = k
or n= 7k
so n is a multiple of 7 and not necessarily a prime....
only when k =1, it is prime...
when k= 2, it is not prime...
so, statement two give multiple values of k which may or may not be prime...
hence its insufficient

So, the answer is A...
OA please?
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by aagar2003 » Wed Oct 20, 2010 2:07 pm
Here is my answer:

A) n is a factor of 56:
56 = 1*2^3*7 Since n is an odd integer > 1 => n=7 only
B) 14 is a factor of 2n:
14=2*7
=> n=7k for any k >=1
Let's see two possibilities for n
One is n=7 and other n=7*7=49
First one is prime and the second one is not prime. So can't tell whether n is prime or not because it depends.
Therefore, answer is A.
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