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 Post subject: For a finite sequence of non zero numbers, the number
 Post Posted: Fri Jul 17, 2009 3:35 am 
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Students


Posts: 77
For a finite sequence of non zero numbers, the number of variations in the sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1,-3,2,5,-4,-6?

1)1
2)2
3)3
4)4
5)5

i remember when i did this problem for the first time, i re-arranged them in ascending order and got the wrong answer. what part of the question should stop me from doing such mistakes?


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 Post subject: Re: sequence
 Post Posted: Tue Jul 21, 2009 6:10 pm 
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ManhattanGMAT Staff


Posts: 12473
ashish.jere wrote:
i remember when i did this problem for the first time, i re-arranged them in ascending order and got the wrong answer. what part of the question should stop me from doing such mistakes?


you're asking the wrong question. a SEQUENCE, by default, is IN ORDER. you cannot change the order of a sequence unless you are explicitly instructed to do so by the problem.

if the profits of a business, in sequence, for a few consecutive years are $1 million, $4 million, -$2 million, $3 million, and $0, then you can't just rearrange those into increasing order.

the question is, "is there anything here that TELLS me to re-order the sequence?"
the answer is no.
therefore, you don't re-order the sequence.
that's pretty much it.

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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Aug 06, 2009 3:01 am 
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Students


Posts: 22
Hi,

Is the answer B.

My working:

1* -3 = -VE

5*-4 = -VE

Number of variation = 2

hence (B).


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Aug 06, 2009 2:23 pm 
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Students


Posts: 8
Chunkberry, I think the answer is C, three. You missed one pair.
(1, -3), (-3,2) and (5, -4).


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Aug 06, 2009 2:26 pm 
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Students


Posts: 6
I'd go with C. My working:
1*-3 = negative
-3*2 = negative
5*-4 = negative


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Aug 06, 2009 3:51 pm 
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Students


Posts: 7
What about -3*2? I say the answer is C.


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Mon Aug 17, 2009 8:15 pm 
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ManhattanGMAT Staff


Posts: 818
ashish.jere, I think the responses answer your question.

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ManhattanGMAT


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Dec 01, 2011 1:44 am 
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Students


Posts: 14
Questions such as the one mentioned above clearly indicate the "hey did you go through the definition of Sequences" and imprint the idea in your head. Oh also, never be creative and never assume, so if it says "sequence" you may not re arrange it. There are 1000 other questions they could form to test ones ability, such questions just show their lack of interest.

As a student preparing for the GMAT, I would like to be outwitted, then be cheated (If I may put it in that sense).


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Fri Dec 02, 2011 8:03 am 
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Students


Posts: 3
Oh! God What is dis question. I got dis in my GMAT Prep and it took me ages to understand it. It was the 3rd ques in quant sec. It scared me so much that I ended up doing very bad in my Prep test.

Can someone explain in detail what is this ques saying?


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Fri Dec 09, 2011 4:56 am 
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ManhattanGMAT Staff


Posts: 12473
tarunlakhani wrote:
Oh! God What is dis question. I got dis in my GMAT Prep and it took me ages to understand it. It was the 3rd ques in quant sec. It scared me so much that I ended up doing very bad in my Prep test.

Can someone explain in detail what is this ques saying?


hi --

two things, please

(1) please write without abbreviations ("dis", etc.) that make your text difficult to understand;
(2) please ask a more specific question. i.e., what did you understand? what didn't you understand? with what particular part of the wording did you have trouble?
this is a problem in which an unfamiliar term ("variations in sign") is given a definition directly in the problem statement, so, it's essential that we understand exactly what gave you trouble.

thanks.

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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Wed Jan 11, 2012 8:56 am 
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Prospective Students


Posts: 25
can this be a pair 6*-1


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Sun Jan 15, 2012 4:10 pm 
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ManhattanGMAT Staff


Posts: 4838
Location: Southwest Airlines, seat 21C
yes, if 6 showed up in the sequence followed immediately by -1, that would be a pair as defined in the problem..

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Tim Sanders
Manhattan GMAT Instructor


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Thu Mar 01, 2012 5:48 pm 
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Posts: 27
Tim,

So, the answer should be C (i.e 3 variations). Am i right ?

Thanks,
Shubh


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Sat Mar 03, 2012 8:47 am 
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ManhattanGMAT Staff


Posts: 12473
shubham_sagijain wrote:
Tim,

So, the answer should be C (i.e 3 variations). Am i right ?

Thanks,
Shubh


yes.

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On peut poser des questions à Ron en français
Voit esittää kysymyksiä Ron:lle myös suomeksi

Un bon vêtement, c'est un passeport pour le bonheur.
Yves Saint-Laurent


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 Post subject: Re: For a finite sequence of non zero numbers, the number
 Post Posted: Sat Mar 03, 2012 8:49 am 
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Forum Guests


Posts: 27
RonPurewal wrote:
shubham_sagijain wrote:
Tim,

So, the answer should be C (i.e 3 variations). Am i right ?

Thanks,
Shubh


yes.


Thanks Ron !


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