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

Redeem

Series

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Mon Mar 28, 2011 9:35 pm
Thanked: 4 times

Series

by artstudent » Mon Jul 25, 2011 7:00 pm
If the a-th term of a certain sequence is given by (-1)ª + (-0.1)ª, then the sum of the terms from 1 to 5 is

A. -1.11111
B. -1.09091
C. 0
D. 0.90909
E. 1.11111

Quick way to do this?
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 965
Joined: Thu Jan 28, 2010 12:52 am
Thanked: 156 times
Followed by:34 members
GMAT Score:720

by vineeshp » Mon Jul 25, 2011 7:14 pm
I dont know if this is the quick way, but this is my way.

(-1)ª - 3 terms will be negative (i.e. -1) and 2 positive(1). Hence leaving us with sum -1. (this leaves us with just A and B as the sum of the other terms (-0.1)ª cannot take us back to a positive number)

then we have 3 negative terms -(0.1+....) and 2 positive terms (.01 and .00001). A can only be correct if all terms were positive. 0.1 + .01 + .001..

leaving us with just B.
Vineesh,
Just telling you what I know and think. I am not the expert. :)
Top
Post new topic Post Reply
• Page 1 of 1