Register    Login    Search    Rss Feeds

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


 Page 1 of 1 [ 7 posts ] 



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

Which is greater than 2/3?

Author Message
Guest
 Post subject: Which is greater than 2/3?
 Post Posted: Wed Jun 04, 2008 8:02 pm 
[text deleted by Rey - OG problems may not be posted on this forum. Please refer to the sticky about this and other banned problem sources.]

What is the quickest way to solve this problem. The answer is B.
Top 
RonPurewal
 Post subject:
 Post Posted: Thu Jun 05, 2008 6:50 am 
Offline
ManhattanGMAT Staff


Posts: 6765
the quickest way to solve the problem is to use cross products to compare the fractions.
here is a page that explains that process: http://www.mathleague.com/help/fraction ... gfractions

for the correct answer, 8/11, the cross products are 8 x 3 = 24 and 2 x 11 = 22. the 24 wins, so the fraction with the 8 on top (8/11) is the larger fraction.
for all the other comparisons, the cross product headed by the 2 will win, meaning that the 2/3 is the larger fraction.

--

note also that 2/3 = 0.6666..., and all the other answer choices are easily memorized decimals:
1/50 is 0.02, so (a) is 0.66
1/11 is 0.0909090909..., so (b) is 0.7272727272... (i always thought this was cool) - note that you're done as soon as you find this.
1/5 is 0.2, so (c) is 0.6
1/8 is 0.125, so (e) is 0.625
13/17 is a bit of a bear, but you don't have to do it (you'd save it for last because it's ugly, and then you'd discover (b) before having to do it)
Top 
shaji
 Post subject: Re: Which is greater than 2/3?
 Post Posted: Fri Jun 06, 2008 12:17 am 
Guest wrote:

What is the quickest way to solve this problem. The answer is B.


13/17>2/3 as well.
Top 
guest
 Post subject:
 Post Posted: Fri Jun 06, 2008 3:34 am 
I attacked the problem in a little different way:

1. x> 2/3. (need to find x)
2. Convert options with almost similar denominators:

i.e.
8/11= 32/44
3/5= 30/50
13/17= 39/51
5/8= 30/48

My intution when comparing goes for 13/17 (bigger numerator). Hence i compared it with 2/3 with common denominator and found 13/17 >2/3.

It didn't take moe than 2 mins to crack this
Top 
rfernandez
 Post subject:
 Post Posted: Fri Jun 06, 2008 4:50 am 
Offline
Course Students


Posts: 386
There must be a typo in the original post, as we have two correct choices.

Also, Guest, did you actually see this problem on a GMAT Prep exam? Please confirm the source. Thanks.
Top 
Guest
 Post subject:
 Post Posted: Sun Jun 08, 2008 5:12 am 
Also 13/17 x 6/6 = 78/102

Kevin Armstrong
Madrid, Spain
Top 
rfernandez
 Post subject:
 Post Posted: Fri Jun 13, 2008 4:09 am 
Offline
Course Students


Posts: 386
As Guest did not respond, I deleted the original post's contents. This problem is from the OG and posting it here violates our guidelines. Thanks for your understanding and cooperation.
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 7 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: