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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Sums and what not?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 71
Joined: Tue Mar 03, 2009 1:24 pm
by coolgirl26 » Sun Apr 12, 2009 2:06 pm
how do you get the answer for this

i used the sum formula and plugged in
1st ter=1/2
last term = 1/1024

into sums formula..so it should be greater than 2..
but why am i getting it wrong
Attachments
ok yo.jpg
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 92
Joined: Wed Mar 25, 2009 12:13 pm
Thanked: 10 times

by moutar » Sun Apr 12, 2009 2:57 pm
You are getting it wrong because there are alternating signs.

This is one way you could look at it. There are others.

T = 1/2 - 1/4 + 1/8 - 1/16 + 1/32 - 1/64 + ...
= (1/2 - 1/4) + (1/8 - 1/16) + (1/32 - 1/64) + ...
= 1/4 + 1/16 + 1/64 + ...

This sum will be a little bit more than a quarter. Thus answer D.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members
Location: India
Thanked: 267 times
GMAT Score:760

by sanju09 » Mon Apr 13, 2009 2:27 am
moutar wrote:You are getting it wrong because there are alternating signs.

This is one way you could look at it. There are others.

T = 1/2 - 1/4 + 1/8 - 1/16 + 1/32 - 1/64 + ...
= (1/2 - 1/4) + (1/8 - 1/16) + (1/32 - 1/64) + ...
= 1/4 + 1/16 + 1/64 + ...

This sum will be a little bit more than a quarter. Thus answer D.
this in fact forms a geometric progression whose first tem and common ratio is each 1/4, since the common ratio is between 0 and 1, hence the sum to an infinite number of such terms would still be finite and will be equal to (1/4)/[1 - (1/4)] = 1/3. Choose the most suitable interval.
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1