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

Redeem

Number Systems

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 202
Joined: Sun Sep 08, 2013 11:51 am
Thanked: 3 times
Followed by:2 members

Number Systems

by sukhman » Tue Oct 15, 2013 9:44 am
For a finite sequence of nonzero 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 is in sign for the sequence: 1, -3, 2, 5, -4, -6?
Top
Source: — Problem Solving |

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 » Tue Oct 15, 2013 9:47 am
sukhman wrote:For a finite sequence of nonzero 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 is in sign for the sequence: 1, -3, 2, 5, -4, -6?
A. 1
B. 2
C. 3
D. 4
E. 5

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

Let's examine the pairs of consecutive terms:

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
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Tue Oct 15, 2013 9:50 am
1 x -3 = "-3"
-3 x 2 = "-6"
2 x 5 = 10
5 x -4 = "-20"
-4 x -6 = 24

Answer [spoiler]{3}[/spoiler]
R A H U L
Top
Post new topic Post Reply
• Page 1 of 1