Register    Login    Search    Rss Feeds

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


 Page 1 of 1 [ 5 posts ] 



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

PS: GCD

Author Message
cesar.rodriguez.blanco
 Post subject: PS: GCD
 Post Posted: Sun Aug 16, 2009 8:34 pm 
Offline
Course Students


Posts: 145
What is the greatest common divisor of positive integers m and n?
1) m is a prime number
2) 2n=7m

I missed this question. Can m=n?
Top 
selva.e
 Post subject: Re: PS: GCD
 Post Posted: Mon Aug 17, 2009 1:43 am 
Offline
Students


Posts: 60
i dont think m = n since both are integers.

1) m is prime INSUFF. didn't tell anything about n .

2) 2n = 7m
this tells something about m and n.

but n will be multiple of 7 and m will muliples of 2. to make aboev stmt true. So we get infinite GCD. insuff.

combine both,

if m is prime, then it should be 2, to make the 2n = 7m true.
So if m = 2, then n = 7

so gcd(2,7) can be found. SO C.
Top 
RonPurewal
 Post subject: Re: PS: GCD
 Post Posted: Tue Sep 15, 2009 6:33 pm 
Offline
ManhattanGMAT Staff


Posts: 7146
cesar.rodriguez.blanco wrote:
What is the greatest common divisor of positive integers m and n?
1) m is a prime number
2) 2n=7m

I missed this question. Can m=n?


(1)
you should still find the values that prove this statement insufficient.

if m = 3 (which is prime) and n = 6, then the gcf is 3.
if m = 3 (which is prime) and n = 5, then the gcf is 1.
insufficient.

(2)

if you have a statement like this - number * variable = other number * other variable - then you should recognize it as a RATIO.
to change it into RATIO form, divide by one of the numbers, and divide by the other variable (i.e., the variable that doesn't have this number as a coefficient).

in the case of this statement, you can divide by 2m on both sides, to give n/m = 7/2. (you could also divide by 7n, to give m/n = 2/7.)

so, the ratio of n to m is 7:2.
if they're actually 7 and 2, the gcf is 1.
if they're multiples of these numbers, then the gcf is not 1. (for instance, if they're 14 and 4, the gcf is 2.)
insufficient.

--

(together)
if you need a prime, and the ratio is 7 to 2, then the numbers must actually be 7 and 2.
sufficient.
Top 
bawies00
 Post subject: Re: PS: GCD
 Post Posted: Thu Jan 05, 2012 11:44 pm 
Offline
Forum Guests


Posts: 1
Is it not possible to say, when using statement 2 only, that the GCF will be 1/2*m ?
Top 
tim
 Post subject: Re: PS: GCD
 Post Posted: Sun Jan 15, 2012 4:00 pm 
Offline
ManhattanGMAT Staff


Posts: 2242
Location: Southwest Airlines, seat 21C
sure. and since you don't know what m is, the statement is insufficient..

_________________
Tim Sanders
Manhattan GMAT Instructor
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 5 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: