Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » GMAT Prep Math


 Page 1 of 1 [ 4 posts ] 



  Print view Print view Previous topic Previous topic | Next topic Next topic
 

If K is a positive integer...

Author Message
michael.thorsen
 Post subject: If K is a positive integer...
 Post Posted: Thu May 20, 2010 3:33 pm 
Offline
Course Students


Posts: 2
If K is a positive integer, is K the square of an integer?
1)K is divisible by 4
2)K is divisible by exactly four different prime numbers

OA=E

I was confused by statement 2. Four different prime numbers-does that mean four total (and different) as in [2,3,5,7] or can that mean [2,2,3,3,5,5,7,7]
Top 
RonPurewal
 Post subject: Re: If K is a positive integer...
 Post Posted: Sun May 23, 2010 6:28 am 
Offline
ManhattanGMAT Staff


Posts: 6765
michael.thorsen wrote:
If K is a positive integer, is K the square of an integer?
1)K is divisible by 4
2)K is divisible by exactly four different prime numbers

OA=E

Quote:
I was confused by statement 2. Four different prime numbers-does that mean four total (and different) as in [2,3,5,7] or can that mean [2,2,3,3,5,5,7,7]


it means the latter.
(statements about divisibility do not determine how many times a given factor will go into a number; they only determine whether that factor will go into the number.)

--

notice that you can actually figure this out, if you recall that the two statements never contradict each other on a data sufficiency problem.

specifically, note that statement (1) requires the presence of TWO "2"s in the prime factorization of k. since this statement is not allowed to contradict statement (2), your first possible interpretation above is ruled out.
Top 
s.aamershah
 Post subject: Re: If K is a positive integer...
 Post Posted: Sat May 29, 2010 6:01 pm 
Offline
Students


Posts: 20
I want to make sure I understand the answer. Because b) can mean k= (2,2,3,3,5,5,7,7) and this also satisfies a) the resulting answer is a perfect square because all the prime factors are in pairs and the answer to the question is "k the square of an integer" is yes

BUT b) can also mean k= (2,2,2,3,3,3,5,5,5,7,7,7) in which case this still satisfies a) but this is actually a perfect cube since all the factors are in groups of three and in this case the answer the to the question is "k the square of an integer" is no.

Is this why the answer is E) ?
Top 
mschwrtz
 Post subject: Re: If K is a positive integer...
 Post Posted: Sat Jun 12, 2010 1:10 am 
Offline
ManhattanGMAT Staff


Posts: 506
yes, well-put.
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 4 posts ] 





Who is online

Users browsing this forum: No registered users and 1 guest

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: