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Tough or stupid DS question ?

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Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 02:05
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100% (04:17) correct 0% (00:00) wrong based on 0 sessions
Hi,

First of all, You need to know I score between 47 and 50 in quant. This question should be then, I guess, a 650 score question.

I answered D because I thought A & B was suffiscient to answer the question but it seems that B is not.
Could you please explain? I Probably missed a thing, but I don't know what :)

Thank you very much. This is probably stupid but I don't know why B is not suff.
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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 02:23
pierrealexandre77 wrote:
Hi,

First of all, You need to know I score between 47 and 50 in quant. This question should be then, I guess, a 650 score question.

I answered D because I thought A & B was suffiscient to answer the question but it seems that B is not.
Could you please explain? I Probably missed a thing, but I don't know what :)

Thank you very much. This is probably stupid but I don't know why B is not suff.


The reason is that n cancels out in (1):

[(n/3)*(6f+2½i)+(2n/3)*(5f+10i)]/n = (1/3)*(6f+2½I)+(2/3)*(5f+10i) = a real number.

In (2) we have one eq. in two unknowns:

(178f+9i)/n= ?
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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 02:31
That's pretty interesting...

I thought having a result like 180/n was a good one...

We must get rid of the N ??? and have a real number????
Please confirm this... I'm going to check on my books too, because I was not aware of this rule

I though 180/n was enough to have the information as N is a part of the question.
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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 03:54
pierrealexandre77 wrote:
That's pretty interesting...

I thought having a result like 180/n was a good one...

We must get rid of the N ??? and have a real number????
Please confirm this... I'm going to check on my books too, because I was not aware of this rule

I though 180/n was enough to have the information as N is a part of the question.


Indeed. Unless the question explicitly asks something like: What its the average "in terms of N" you should always look for an actual answer.
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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 04:31
This indeed changes everything.

Thank you andershv :)

Have a nice day
Alex
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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 06:32
I had similar doubts when I first started working on DS... but as we work we understand and also learn techniques to eliminate choices ..

if A is sufficient then answer must be A or D
if A is insufficient, then answer must be B,C or E
if B is sufficient then answer must be B or D
if B is insufficient then answer must be A,C,E
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Thanks, Sri
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keep uppp...ing the tempo...

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Re: Tough or stupid DS question ? [#permalink] New post 27 Oct 2009, 08:27
pierrealexandre77 wrote:
This indeed changes everything.

Thank you andershv :)

Have a nice day
Alex


Glad to be of assistance :-). You have a nice day as well...
Re: Tough or stupid DS question ?   [#permalink] 27 Oct 2009, 08:27
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