Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » Official Guide Math


 Page 1 of 1 [ 4 posts ] 



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

OG - DS - #146

Author Message
benahavis
 Post subject: OG - DS - #146
 Post Posted: Sun Apr 15, 2007 1:24 pm 
Please explain the following question (#146 in the OG 11th addition):

Is n an integer?

(1) n^2 is an integer.
(2) The square root of n is an integer. [Not sure how to write the square root symbol]

The Official Guide says the answers is B. I don't understand why the answer isn't D.
Top 
tali62
 Post subject:
 Post Posted: Sun Apr 15, 2007 6:59 pm 
(square root of m)^2 = m where m is an integer but not a perfect square.
it doesn't imply that "square root of m" is also an integer.
Top 
Guest
 Post subject:
 Post Posted: Sun Apr 15, 2007 10:38 pm 
Benahavis,

In addition to tali62's explanation, you can also use examples (trial and error) to prove that statement (1) is insufficient.

For example,

If n = 2, then n^2 = 4.
If n = 1.414...., then n^2 = 2.

Therefore, n could be either an integer or a non-integer, which makes statement (1) alone insufficient.

Seeing as you initially thought D was the answer, you already know statement (2) is sufficient.

Hope this helps.
Top 
Guest
 Post subject:
 Post Posted: Sun Apr 15, 2007 10:44 pm 
Thanks!
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: