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

Redeem

Sequence

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 49
Joined: Thu Aug 26, 2010 11:08 pm
Thanked: 2 times

Sequence

by narik11 » Sat Sep 25, 2010 11:18 pm
For every positive integer n, if the nth term of the sequence is Xn=1/(n+1)(n+2)
then X1+X2+...X5=?
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pm
Location: Milpitas, CA
Thanked: 447 times
Followed by:88 members

by Rahul@gurome » Sun Sep 26, 2010 12:30 am
Xn = 1/(n+1)(n+2) = 1/(n+1) - 1/(n+2).
So x1 = ½ - 1/3.
X2 = 1/3 - ¼.
X3 = ¼ - 1/5.
X4 = 1/5 - 1/6
X5 = 1/6 - 1/7.

Or x1+x2+x3+x4+x5 = ½ - 1/7 = 5/14.
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
Post new topic Post Reply
• Page 1 of 1