Find all School-related info fast with the new School-Specific MBA Forum

It is currently 18 Apr 2014, 13:00

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

What is the sum of n terms of the series 1/2 + 3/4 + 7/8 +

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Joined: 30 Aug 2003
Posts: 330
Location: BACARDIVILLE
Followers: 1

Kudos [?]: 0 [0], given: 0

GMAT Tests User
What is the sum of n terms of the series 1/2 + 3/4 + 7/8 + [#permalink] New post 06 Mar 2004, 15:51
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
What is the sum of n terms of the series 1/2 + 3/4 + 7/8 + 15/16 + ...equal to?

a. (2^n)-n-1
b. (2^-n)+n-1
c. (2^n)-1
d. (2^2n)-1
e. :ouch
_________________

Pls include reasoning along with all answer posts.
****GMAT Loco****
Este examen me conduce jodiendo loco

Senior Manager
Senior Manager
User avatar
Joined: 30 Aug 2003
Posts: 330
Location: BACARDIVILLE
Followers: 1

Kudos [?]: 0 [0], given: 0

GMAT Tests User
 [#permalink] New post 06 Mar 2004, 16:10
:shock:

reasoning pls
_________________

Pls include reasoning along with all answer posts.
****GMAT Loco****
Este examen me conduce jodiendo loco

Senior Manager
Senior Manager
User avatar
Joined: 06 Dec 2003
Posts: 366
Location: India
Followers: 1

Kudos [?]: 1 [0], given: 0

GMAT Tests User
 [#permalink] New post 07 Mar 2004, 07:16
Quote:
What is the sum of n terms of the series 1/2 + 3/4 + 7/8 + 15/16 + ...equal to?

a. (2^n)-n-1
b. (2^-n)+n-1
c. (2^n)-1
d. (2^2n)-1
e.


Series can be written as:
(2^n - 1) / (2^n) where n runs from 1 to n
Now sum of this series is:

=sum of(1-1/(2^n))
=sum of 1 - sum of (1/(2^n)),
where sum of 1 gives n and
Now, 1/(2^n) is geometric series with a=1/2 and r=1/2
gives sumation as,
a(1-r^n)/(1-r) = (1/2)(1-(1/2)^n)/(1-1/2) = 1 - 2^(-n)
So the answer should be:
n - (1 - 2 ^ (-n))
= 2^-n + n -1

That is B

Hope, i am clear enough

dharmin
  [#permalink] 07 Mar 2004, 07:16
    Similar topics Author Replies Last post
Similar
Topics:
Popular new posts Find the the sum of the first 20 terms of this series which Antmavel 14 13 Mar 2005, 18:19
Popular new posts 2 Find the the sum of the first 20 terms of this series which MBAlad 16 02 Dec 2006, 19:03
New posts Find the sum of the first 20 terms of the series: 1^2 + 2^2 oops 5 04 Jul 2007, 16:25
New posts the sum 7/8 + 1/9 is between a. 1/2 & 3/4 b. 3/4 & 1 r019h 7 22 Aug 2007, 18:26
New posts how do we find the sum of n terms of series : (1^2) + (1^2 earthwork 8 29 Oct 2008, 20:01
Display posts from previous: Sort by

What is the sum of n terms of the series 1/2 + 3/4 + 7/8 +

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.