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 →

find th sum

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 1578
Joined: Sun Dec 28, 2008 1:49 amFollowed by: 9 members
Thanked: 82 times
GMAT Score:720
by maihuna » Mon May 11, 2009 9:46 am
Find the sum of all numbers between 200 and 400 which are divisible by 7.

8428
8548
8673
8729
9879

Find the sum of integers from 1 to 100 that are divisible by 2 or 5.

2550
3050
3240
3300
3600

Find the sum of all two digit numbers which when divided by 4, yields 1 as
remainder.

1076
1150
1210
1250
1340
Charged up again to beat the beast :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Legendary Member
Posts: 1035
Joined: Wed Aug 27, 2008 10:56 pmFollowed by: 1 member
Thanked: 104 times

by scoobydooby » Mon May 11, 2009 10:18 am
Q1. number of integers between 200 and 400=199
number of integers divisible by 7=>199/7=28

set of integers: 203, 210......399
sum of the integer set: 28*(203+399)/2=301*28=8428
hence, A


Q2. sum of integers from 1 to 100 divisble by 2
=2+4+6+8+.....+100
=2(1+2+...+50)
=2*50*51/2=2550........a

sum of integers from 1 to 100 divisble by 5
=5+10+15+...+100
=5(1+2+2...+20)
=5*20*21/2=5*10*21=1050.....b

sum of integers divisibe by 2 or 5
=2550+1050
=3600
hence, E


Q3. 2 digit numbers which leave a remainder 1 when divided by 4
of the form 4k+1, k must take values 3, 4, .....,24 as we only need 2 digit numbers

set of numbers: 13+17+21+....+97

Tn=97=13+(n-1)4, solving for n we get n=22

mean of the set: (13+97)/2=110/2=55

sum of the set: 55*22=1210
hence, C
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 3
Joined: Thu Apr 09, 2009 8:39 am

by hawlia » Mon May 11, 2009 10:28 am
scoobydooby wrote:Q1. number of integers between 200 and 400=199
number of integers divisible by 7=>199/7=28

set of integers: 203, 210......399
sum of the integer set: 28*(203+399)/2=301*28=8428
hence, A


Q2. sum of integers from 1 to 100 divisble by 2
=2+4+6+8+.....+100
=2(1+2+...+50)
=2*50*51/2=2550........a

sum of integers from 1 to 100 divisble by 5
=5+10+15+...+100
=5(1+2+2...+20)
=5*20*21/2=5*10*21=1050.....b

sum of integers divisibe by 2 or 5
=2550+1050
=3600
hence, E


Q3. 2 digit numbers which leave a remainder 1 when divided by 4
of the form 4k+1, k must take values 3, 4, .....,24 as we only need 2 digit numbers

set of numbers: 13+17+21+....+97

Tn=97=13+(n-1)4, solving for n we get n=22

mean of the set: (13+97)/2=110/2=55

sum of the set: 55*22=1210
hence, C
Acc to me Ans of First Ques is 8729
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Mon May 11, 2009 11:02 am
scoobydooby wrote:Q2. sum of integers from 1 to 100 divisble by 2
=2+4+6+8+.....+100
=2(1+2+...+50)
=2*50*51/2=2550........a

sum of integers from 1 to 100 divisble by 5
=5+10+15+...+100
=5(1+2+2...+20)
=5*20*21/2=5*10*21=1050.....b

sum of integers divisibe by 2 or 5
=2550+1050
=3600
hence, E
Except that you've double counted 10, 20, 30, ... 100, which are divisible by both 2 AND 5.

So, we have to subtract the multiples of both 2 and 5.

3600 - (10 + 20 + 30 + ... + 100)

= 3600 - 10(55) = 3600 - 550 = 3050... choose (B).

[The shortcut I used to calculate that series, which could have been used on all of these questions (and which Scooby did use), is merely an application of the average forumla.

Sum of terms = (# of terms)(average)

For a set of consecutive numbers, the average is simply:

(1st # + Last #)/2

or in this case:

(10 + 100)/2 = 110/2 = 55]
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 73
Joined: Wed Jan 07, 2009 1:00 pm
Location: Tampa, FL
Thanked: 9 times
GMAT Score:630

by Mr2Bits » Mon May 11, 2009 11:25 am
hawlia wrote:
scoobydooby wrote:Q1. number of integers between 200 and 400=199
number of integers divisible by 7=>199/7=28

set of integers: 203, 210......399
sum of the integer set: 28*(203+399)/2=301*28=8428
hence, A


Q2. sum of integers from 1 to 100 divisble by 2
=2+4+6+8+.....+100
=2(1+2+...+50)
=2*50*51/2=2550........a

sum of integers from 1 to 100 divisble by 5
=5+10+15+...+100
=5(1+2+2...+20)
=5*20*21/2=5*10*21=1050.....b

sum of integers divisibe by 2 or 5
=2550+1050
=3600
hence, E


Q3. 2 digit numbers which leave a remainder 1 when divided by 4
of the form 4k+1, k must take values 3, 4, .....,24 as we only need 2 digit numbers

set of numbers: 13+17+21+....+97

Tn=97=13+(n-1)4, solving for n we get n=22

mean of the set: (13+97)/2=110/2=55

sum of the set: 55*22=1210
hence, C
Acc to me Ans of First Ques is 8729
Different way to work the first is as follows.

1/2*28*(7(29+57))
= 8428
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 1578
Joined: Sun Dec 28, 2008 1:49 amFollowed by: 9 members
Thanked: 82 times
GMAT Score:720

by maihuna » Tue May 12, 2009 9:23 am
OA:
8729
3050 Thanks Stuart
1210
Charged up again to beat the beast :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1