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ashish.jere
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For a finite sequence of non zero numbers, the number

by ashish.jere Fri Jul 17, 2009 3:35 am

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?
RonPurewal
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Re: sequence

by RonPurewal Tue Jul 21, 2009 6:10 pm

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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chuckberry007
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Re: For a finite sequence of non zero numbers, the number

by chuckberry007 Thu Aug 06, 2009 3:01 am

Hi,

Is the answer B.

My working:

1* -3 = -VE

5*-4 = -VE

Number of variation = 2

hence (B).
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Re: For a finite sequence of non zero numbers, the number

by elaine1920 Thu Aug 06, 2009 2:23 pm

Chunkberry, I think the answer is C, three. You missed one pair.
(1, -3), (-3,2) and (5, -4).
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Re: For a finite sequence of non zero numbers, the number

by adam.roffman Thu Aug 06, 2009 2:26 pm

I'd go with C. My working:
1*-3 = negative
-3*2 = negative
5*-4 = negative
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Re: For a finite sequence of non zero numbers, the number

by sharath.nair Thu Aug 06, 2009 3:51 pm

What about -3*2? I say the answer is C.
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Re: For a finite sequence of non zero numbers, the number

by Ben Ku Mon Aug 17, 2009 8:15 pm

ashish.jere, I think the responses answer your question.
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Re: For a finite sequence of non zero numbers, the number

by karanrob Thu Dec 01, 2011 1:44 am

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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Re: For a finite sequence of non zero numbers, the number

by tarunlakhani Fri Dec 02, 2011 8:03 am

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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Re: For a finite sequence of non zero numbers, the number

by RonPurewal Fri Dec 09, 2011 4:56 am

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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Re: For a finite sequence of non zero numbers, the number

by amit1234 Wed Jan 11, 2012 8:56 am

can this be a pair 6*-1
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Re: For a finite sequence of non zero numbers, the number

by tim Sun Jan 15, 2012 4:10 pm

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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Re: For a finite sequence of non zero numbers, the number

by shubham_sagijain Thu Mar 01, 2012 5:48 pm

Tim,

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

Thanks,
Shubh
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Re: For a finite sequence of non zero numbers, the number

by RonPurewal Sat Mar 03, 2012 8:47 am

shubham_sagijain wrote:Tim,

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

Thanks,
Shubh


yes.
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Re: For a finite sequence of non zero numbers, the number

by shubham_sagijain Sat Mar 03, 2012 8:49 am

RonPurewal wrote:
shubham_sagijain wrote:Tim,

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

Thanks,
Shubh


yes.


Thanks Ron !