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 Post subject: DS Power prep
 Post Posted: Mon Aug 18, 2008 2:42 pm 
Each employee of Company Z is an employee of either Division X or Division Y, but not both. If each division has some part-time employees, is the ratio of the number of full-time employees to the number of part-time employees greater for Div X than for Company Z?

(1) The ratio of the number of full-time employees to the number of part-time employees is less for Div Y than for Company Z.
(2) More than half of the full-time employees of Company Z are employees of Div X, and more than half of the part-time employees of Company Z are employees of Div Y

OA is D. Someone please explain. Thank you!


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 Post subject:
 Post Posted: Mon Aug 25, 2008 6:09 am 
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ManhattanGMAT Staff


Posts: 7146
(1)
remember that ratios are the same as fractions in this sort of context.
this statement means that the FT employees are a smaller fraction of division Y than of the company as a whole. this means that they must be a bigger fraction of division X than of the company as a whole, because the fraction of the whole company that's employed FT must be between the two divisions' fractions.
sufficient.

(analogy: if i mix two powders together to make a shake that's 5% fat, and the first powder is 3% fat, then the second powder must be more than 5% fat)

--

(2)
the first part means that (FT in div. X) > (FT in div. Y), and the second part means that (PT in div. X) < (PT in div. Y).
therefore, considering the ratio of FT : PT for each division, we have that FT/PT for div. X must be greater than FT/PT for div. Y. (this is the case because of either the numerator or the denominator: the numerator of X is greater, and the denominator is smaller.)
since the FT/PT fraction is bigger for div. X than for div. Y, it must be bigger for div. X than for the company as a whole (see the reasoning above under statement (1) for why this is true).
sufficient.


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 Post subject: Great explanation Ron!
 Post Posted: Tue Aug 26, 2008 2:17 pm 
I think I was overwhelmed during the exam with the length of the question. After seeing your explanation I don't understand why I couldn't solve it.
Many thanks!!!


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 Post subject: Re:
 Post Posted: Sun Sep 18, 2011 4:29 pm 
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Students


Posts: 23
Location: Bangalore
RonPurewal wrote:
(1)
remember that ratios are the same as fractions in this sort of context.
this statement means that the FT employees are a smaller fraction of division Y than of the company as a whole. this means that they must be a bigger fraction of division X than of the company as a whole, because the fraction of the whole company that's employed FT must be between the two divisions' fractions.
sufficient.

(analogy: if i mix two powders together to make a shake that's 5% fat, and the first powder is 3% fat, then the second powder must be more than 5% fat)

I'm not able to clearly understand this part. Could you please explain with a much more elaborate example.


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 Post subject: Re: Re:
 Post Posted: Tue Sep 20, 2011 7:39 am 
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ManhattanGMAT Staff


Posts: 7146
linzphilipv wrote:
I'm not able to clearly understand this part. Could you please explain with a much more elaborate example.


1/
for us to help you, you'll have to specify what you didn't understand.

2/
what do you mean by “much more elaborate”?
i'll assume you don't actually mean elaborate, because an example that's actually elaborate, by definition, will be harder to understand than an example that's simple.


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 Post subject: Re: DS Power prep
 Post Posted: Thu Oct 27, 2011 7:30 am 
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Students


Posts: 33
pick number to do this fast

100=30-fx+10-fy+20-px+40-py

30= number full time of x division.

finish in 1 minutes.


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 Post subject: Re: DS Power prep
 Post Posted: Wed Nov 09, 2011 6:52 am 
Offline
ManhattanGMAT Staff


Posts: 7146
namnam123 wrote:
pick number to do this fast

100=30-fx+10-fy+20-px+40-py

30= number full time of x division.

finish in 1 minutes.


whoa, that doesn't work. you can't pick ONE VALUE for a data sufficiency problem, and then think you're done!
if you do that, you'll think that every statement is always sufficient.

it is possible to use number plugging on data sufficiency, but you have to plug in MULTIPLE possible values.
if you keep getting the same answer with all of your plug-ins, then the statement is sufficient.
if two of your different plug-ins give two different answers -- clearly something that can never happen with one plug-in -- then the statement is insufficient.


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