Number of variations

[xxslilangelxx]

I am not really familiar with number of variation materials, would anybody help me explain the answer?

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<--- correct answer
D. 4
E. 5

[Brent@GMATPrepNow]

I am not really familiar with number of variation materials, would anybody help me explain the answer?

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<--- correct answer
D. 4
E. 5

Aside: Please use the spoiler function to hide the answers. This will allow others to try the question as well.

I had to read this one twice

We're asked to look at every pair of consecutive numbers. If the product of that pair is negative, this counts as one variation.

Let's examine the pairs of consecutive numbers:

1 and -3: product is negative
-3 and 2: product is negative
2 and 5: product is positive
5 and -4: product is negative
-4 and -6: product is positive

Since 3 pairs have negative products, the correct answer is C

Cheers,
Brent