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Question from GmatPrep

by saidov.mikhail » Wed Oct 02, 2013 11:51 pm
For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consequtive terms of sequence for which the product of the two consequtive 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
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by theCodeToGMAT » Wed Oct 02, 2013 11:57 pm
1,-3

-3,2

5,-4

Hence, three
Answer {C}
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by [email protected] » Thu Oct 03, 2013 12:32 am
Hi saidov.mikhail,

This is an example of a symbolism question (it just doesn't have a physical symbol in it). We're told that a "variation" occurs when the PRODUCT of two consecutive integers is NEGATIVE.

With the given sequence: 1, -3, 2, 5, -4, -6.....

We need to count up the number of times that a "variation" occurs.

Working through each pair of consecutive numbers:
(1)(-3) = -3 YES
(-3)(2) = -6 YES
(2)(5) = 10 NO
(5)(-4) = -20 YES
(-4)(-6) = 24 NO

Here, we have 3 "variations".
Final Answer: C

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