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sequence of nonzero numbers

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by LevelOne » Fri Jul 03, 2009 12:07 pm
For a finite sequence of nonzero numbers, the number of variations in 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?

A. one
B. two
C. three
D. four
E. five

sounds simple :? ? I'm not sure if I understand it correctly...

I rearrange to have the consecutive terms {-6,-4,-3,1,2,5}. Does it make sense to pair each negative number with a positive one to get the number of variations in sign? thanks
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Re: sequence of nonzero numbers

by rahulg83 » Fri Jul 03, 2009 12:11 pm
LevelOne wrote:For a finite sequence of nonzero numbers, the number of variations in 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?

A. one
B. two
C. three
D. four
E. five

sounds simple :? ? I'm not sure if I understand it correctly...

I rearrange to have the consecutive terms {-6,-4,-3,1,2,5}. Does it make sense to pair each negative number with a positive one to get the number of variations in sign? thanks
Hi again,
well u don't have to rearrange the series. let it be as it is. :)Please make sure that you don' rearrange any series unless said to do so (in median calculations for example)
No of variations = 3, is this the answer?
1*-3
-3*2
5*-4
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by LevelOne » Fri Jul 03, 2009 12:14 pm
that's what I thought! thanks for confirming, OA is C.
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by LevelOne » Fri Jul 03, 2009 12:17 pm
rahulg83, i just noticed something...why are you using -3 twice?? does it suppose to be -6 instead?

1*-3
-3*2
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by rahulg83 » Fri Jul 03, 2009 12:35 pm
Nopes..
We want to know what is the number of variations in sign for the sequence.
there would be three of them...

1, -3, 2, 5, -4, -6

1, -3, 2, 5, -4, -6

1, -3, 2, 5, -4, -6
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by LevelOne » Fri Jul 03, 2009 12:48 pm
OK, got it now ;)
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by Strongt » Mon May 02, 2011 4:16 am
Hi,

I got this question on my TestPrep as well. I was stumped, I knew it was very easy but I had no clue what to do!!
What's a good strategy to deal with those kind of questions
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