For a finite sequence of non zero numbers, the number of variations in sign is defined as the number of pairs of...

[BTGmoderatorLU]

Source: GMAT Prep

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

The OA is C

[Brent@GMATPrepNow]

Source: GMAT Prep

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

The OA is C

We're asked to examine every pair of consecutive terms. If the product of those two terms is negative, this counts as one variation.

Let's examine the pairs of consecutive terms in the sequence 1, -3, 2, 5, -4, -6

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 of consecutive terms have negative products, the correct answer is C

Cheers,
Brent