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

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Re: For a finite sequence of non zero numbers, the number of  [#permalink]

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New post 22 Mar 2017, 09:44
TomB wrote:
For a finite sequence of non zero 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. 1
B. 2
C. 3
D. 4
E. 5



We are given the following sequence of numbers: 1, -3, 2, 5, -4, -6.

Every time a pair of consecutive terms product a negative product we have a “variation in sign”. We must determine how many variations in sign are in the sequence.

1 x (-3) = -3, so this is a variation in sign

(-3) x 2 = -6, so this is a variation in sign

5 x (-4) = -20, so this is a variation in sign

Thus, there is a total of 3 variations in sign.

Answer: C
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Re: For a finite sequence of non zero numbers, the number of  [#permalink]

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New post 17 Oct 2018, 01:34
TomB wrote:
For a finite sequence of non zero 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. 1
B. 2
C. 3
D. 4
E. 5


One of the major error I did in this problem was to arrange the terms in ascending order since it was talking about consecutive terms.

For people who did a similar mistake Ron from MGMAT says:

RON: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.

Rest this problem is a cake walk.

Press Kudos if it helps!!
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Re: For a finite sequence of non zero numbers, the number of &nbs [#permalink] 17 Oct 2018, 01:34

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