• Board contributors include instructors with "800" GMAT scores.
  • 95% of posts have replies within 24 hours.
  • Join for discounts with 800score, VeritasPrep and ManhattanGMAT


FAQ  - Register  - Search - Login 

All times are UTC - 7 hours




Post new topic Reply to topic  [ 6 posts ] 
Author Message
 Post subject: GMAT Data Analysis
PostPosted: Thu Jul 26, 2012 11:26 pm 
Offline
User avatar

Joined: Tue Apr 13, 2010 8:48 am
Posts: 483
Image

A computer retailer sells only TFT and LCD style monitors. According to the graph above, where the x-axis represents the day of the week and the y-axis represents the number of monitors sold, on which day was the ratio of the number of LCD monitors sold to total number of monitors sold the greatest?
A. Monday
B. Tuesday
C. Wednesday
D. Thursday
E. Friday

(C) The number of LCD sales is the difference between total sales and TFT sales. For each day of the week, we can determine the ratio of the number of LCD monitors sold to the total number of monitors sold:
Monday: (18 – 10)/18 = 4/9
Tuesday: (22 – 12)/22 = 5/11
Wednesday: (24 – 12)/24 = 1/2
Thursday: (26 – 16)/26 = 5/13
Friday: (26 – 14)/26 = 6/13.

The greatest fraction is 1/2, so the ratio on Wednesday is the largest.The correct answer is choice (C).
-------------

* let L represent the number of LCD monitors sold
* let T represent the number of TFT monitors sold
Why is the ratio calculated as (L-T)/L? I would expect it to be L/(L+T).

Thanks
Top
 Profile  
 
 Post subject: Re: GMAT Data Analysis
PostPosted: Thu Jul 26, 2012 11:32 pm 
Offline
User avatar

Joined: Fri Apr 09, 2010 2:11 pm
Posts: 459
Quote:
Why is the ratio calculated as (L-T)/L? I would expect it to be L/(L+T).

Please, note, that the blue line is "TOTAL sales" line, not "LCD sales" one.

The ratio is calculated (using your denotation):
[(L + T) -T] / (L + T), where (L + T) is the total sales amount.
Let us simplify:
L / (L + T)

But the number of LCD monitors sold is not directly given in the chart. So we have Total and TFT values. Thus we use the formula
(TotalTFT) / Total

As you can see it is the same as L / (L + T), where L = Total – TFT and Total = L + T.


Top
 Profile  
 
 Post subject: Re: GMAT Data Analysis
PostPosted: Thu Jul 26, 2012 11:35 pm 
Offline
User avatar

Joined: Tue Apr 13, 2010 8:48 am
Posts: 483
How is half the largest share? Its equal for both LCD and TFT.


Top
 Profile  
 
 Post subject: Re: GMAT Data Analysis
PostPosted: Thu Jul 26, 2012 11:44 pm 
Offline
User avatar

Joined: Fri Apr 09, 2010 2:11 pm
Posts: 459
questioner wrote:
How is half the largest share? Its equal for both LCD and TFT.
We are NOT looking for the day, on which the LCD share was greater than the TFT share. We are looking for the day, on which the LCD daily share was the greatest among all LCD daily shares throughout the week.

Let's approximate fractions with percentages.
Monday: 4/9 ≈ 44.44%
Tuesday: 5/11 ≈ 45.45%
Wednesday: 1/2 = 50%
Thursday: 5/13 ≈ 38.46%
Friday: 6/13 ≈ 46.15%

As you can see the retailer never sold more LCDs than TFTs, but on Wednesday the LCD share was the greatest among the LCD shares throughout the week (On Thursday it was the lowest).


Top
 Profile  
 
 Post subject: Re: GMAT Data Analysis
PostPosted: Sun Aug 04, 2013 5:56 am 
Offline
User avatar

Joined: Tue Apr 13, 2010 8:48 am
Posts: 483
Hi there.

When the question asks for the greatest ratio, I thought that it might have been one of the others, 1/2 is the largest number but the difference between the two values isn't the biggest. eg for every 1 of a there is 2 of b. But with other ans it was for every 4 of a there is 9 of b. Just so I fully understand, could you please explain ways to fully understand what's being asked in the gmat, because I got the maths right, just misinterpreted. Thanks.


Top
 Profile  
 
 Post subject: Re: GMAT Data Analysis
PostPosted: Sun Aug 04, 2013 5:58 am 
Offline
User avatar

Joined: Fri Apr 09, 2010 2:11 pm
Posts: 459
Quote:
When the question asks for the greatest ratio, I thought that it might have been one of the others, 1/2 is the largest number but the difference between the two values isn't the biggest. e.g. for every 1 of a there is 2 of b. But with other ans it was for every 4 of a there is 9 of b.
It seems as "4 out of 9" operates with larger numbers and gives larger quantities. However, in order to compare this fractions, 1/2 and 4/9, you need to use a common denominator. The least common denominator is 18.

1/2 = 9/18
4/9 = 8/18

Now we can easily compare "9 of every 18 monitors" and "8 of every 18 monitors".


Another way is to imagine percentages.
1/2 = 0.50 or "1 of every 2 monitors" tells us about 50% of monitors.
4/9 = 0.44… or "4 of every 9 monitors" tells us approximately about 44% of monitors.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 3 guests


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:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Template made by DEVPPL -
phpBB SEO
 
GMAT(TM) and GMAT CAT (TM) are registered trademarks of the Graduate Management Admission Council(TM). The Graduate Management Admission Council(TM) does not endorse, nor is affiliated in any way with the owner or any content of this site.