BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Number of variations

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Wed Oct 31, 2012 7:35 am

Number of variations

by xxslilangelxx » Wed Oct 31, 2012 7:38 am
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
Top
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Wed Oct 31, 2012 7:52 am
xxslilangelxx wrote: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
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Post new topic Post Reply
• Page 1 of 1