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

Redeem

For a finite sequence of non zero numbers

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 222
Joined: Mon Oct 13, 2008 4:04 pm
Thanked: 3 times
Followed by:2 members

For a finite sequence of non zero numbers

by venmic » Fri Jan 20, 2012 7:32 pm
For a finite sequence of non zero numbers, the number of variations in the 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?

1)1
2)2
3)3
4)4
5)5

3


Why is (1, -3) considerd a set
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Fri Jan 20, 2012 8:04 pm
venmic wrote:For a finite sequence of non zero numbers, the number of variations in the 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?

1)1
2)2
3)3
4)4
5)5

3


Why is (1, -3) considerd a set

We get a negative integer when one term is positive and the other is negative.

1 * -3 = -3
-3 * 2 = -6
5 * -4 = -20

Therefore, required number of variations = 3

The correct answer is [spoiler](3)[/spoiler].
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Thu Dec 29, 2011 11:03 pm

by Ibrohim » Fri Jan 27, 2012 10:32 pm
Thank you very much for the solution. I had the same problem and still do. Could someone please explain why 1 and -3 are consecutive terms while 5 and -6 are not? Actually how do we identify the pair of consecutive terms.
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 406
Joined: Mon Jan 25, 2010 11:36 am
Location: Syracuse, NY
Thanked: 23 times
Followed by:4 members
GMAT Score:740

by tomada » Sat Jan 28, 2012 2:18 pm
In a sequence of 'N' numbers, the set of consecutive terms = (1st term and 2nd term), (2nd term and 3rd term), ......, ( Nth-1 term, Nth term)
I'm really old, but I'll never be too old to become more educated.
Top
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Thu Dec 29, 2011 11:03 pm

by Ibrohim » Tue Jan 31, 2012 10:57 pm
Thank you tomada. I meant pair of consecutive terms in this specific case. Having looked at the problem for nth time I understood the what it was asking for. Actually, easy problem with hard level clothing.
Top
Post new topic Post Reply
• Page 1 of 1