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Is the integer n odd?

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caralodigiani
 Post subject: Is the integer n odd?
 Post Posted: Sun Sep 19, 2010 7:44 pm 
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Posts: 4
GMAT Prep - Cat #2 - Data Sufficiency

Is the integer n odd?
(1) n is divisible 3
(2) 2n is divisible by twice as many positive integers as n

Thank you!
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parthatayi
 Post subject: Re: Is the integer n odd?
 Post Posted: Mon Sep 20, 2010 12:21 am 
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Course Students


Posts: 40
caralodigiani wrote:
GMAT Prep - Cat #2 - Data Sufficiency

Is the integer n odd?
(1) n is divisible 3
(2) 2n is divisible by twice as many positive integers as n

Thank you!


i think the answer is E.
Taking (1) into consideration:
n can be 6 or 9

Considering statement (2):
2n is always divisible by 2n irrespective whether n is odd.

Even by combining both the statements we cannot narrow down whether n is odd.
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gokul_nair1984
 Post subject: Re: Is the integer n odd?
 Post Posted: Mon Sep 20, 2010 4:26 am 
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Students


Posts: 170
parthatayi wrote:
i think the answer is E.
Taking (1) into consideration:
n can be 6 or 9

Considering statement (2):
2n is always divisible by 2n irrespective whether n is odd.

Even by combining both the statements we cannot narrow down whether n is odd.


Nope,The answer looks more like B.
Question Stem: Is the integer n odd?
Statement 2: 2n is divisible by twice as many positive integers as n

Let n=3 --3^1---No. of factors can be given as (1+1)=2
therefore, 2n =6--(2^1)*(3^1)---No of factors=(1+1)*(1+1)=4. Sufficient

Let n=2---No. of factors=2
2n=4---no. of factors =3. Hence n has to be odd for statement 2 and stem to satisfy.

Final iteration, Let n=9. No. of factors =3
Therefore, 2n=18. No. of factors =6.

Therefore,

When odd number n is doubled, 2n has twice as many factors as n.
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tim
 Post subject: Re: Is the integer n odd?
 Post Posted: Sat Sep 25, 2010 7:07 am 
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ManhattanGMAT Staff


Posts: 2242
Location: Southwest Airlines, seat 21C
Thanks, Gokul. In addition to your ending statement, we also need to make the statement that when n is even, 2n does not have twice as many factors. This follows from your line of reasoning as well, when we consider the formula that is used to determine the number of factors an integer has..

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Tim Sanders
Manhattan GMAT Instructor
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