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 →

PS1000, Set 7, 19

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 75
Joined: Tue Jun 12, 2007 5:35 am
Thanked: 2 times

Re: PS1000, Set 7, 19

by hopefully » Mon Sep 24, 2007 10:43 pm
cindyqtran wrote:The sum of the first 100 positive integers is 5,050. What is the sum of the first 200 positive integers?
(A) 10,100
(B) 10,200
(C) 15,050
(D) 20,050
(E) 20,100
Given
1 + 2 + 3 ..... 100 = 5050

1+2 + 3 ..... 200 = 5050 + 101 + 102 ...... 200
=5050 + (1+100) + (2+100) + (3+100) ...... (100 +100)

= 5050 + 100*100 + 1 + 2+3.... 100
= 5050 + 10000 +5050

= 20100
Live every moment ...

<a href="https://www.beatthegmat.com/viewtopic.ph ... target=new> My 730 </a>
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 460
Joined: Sun Mar 25, 2007 7:42 am
Thanked: 27 times

by samirpandeyit62 » Mon Sep 24, 2007 11:27 pm
sum of first 200 nos = n(n+1)/2 (where n is nos od the nos in series =200)

=200(201)/2 = 20100
Regards
Samir
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 124
Joined: Thu Aug 23, 2007 5:11 am
Thanked: 2 times

by gmatguy16 » Tue Sep 25, 2007 7:04 am
and if someone does not know the series formulae here is how we shud solve..i assume we are not supposed to know the formula since they have given the sum of first 100 no's.

1+2+3...+100 = 5050
101=1+100
102=2+100
..........
199=99+100
200=100+100
thus sum of first 200 nos=sum of first 100+sum of first 100+(100*100)
=5050+5050+10000= the answer
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 460
Joined: Sun Mar 25, 2007 7:42 am
Thanked: 27 times

by samirpandeyit62 » Tue Sep 25, 2007 11:42 pm
Ya Gmatguy16 that's the reason why the sum of the first 100 nos is given.
I would personally solve it like u did, 5050 + 5050 +100 *100 (saves a lot of time)
just included the formula coz its really helpful in some problems.
Regards
Samir
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1