Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Gmat Prep Test 1 Avg cost and total sum

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 231
Joined: Mon Jan 07, 2008 9:39 amFollowed by: 1 member
Thanked: 4 times
by khurram » Wed May 28, 2008 6:15 am
What am i doing wrong

2+20/2 and 1+19/2

11*(20-2+1) -10(19-2+1)=19

Ans is 10
You do not have the required permissions to view the files attached to this post.
Top
Join the discussion
Source: — Problem Solving |
Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Tue May 20, 2008 8:05 am

by agatka16 » Wed May 28, 2008 8:12 am
Maybe you could look at it that way:
a=2+4+6+...+20 ==> you have 10 even integers
b=1+3+4+...+19==> you have 10 odd integers

a-b=(2-1)+(4-3)+(6-5)+...+(20-19)==> each term is 1 and you have 10 terms. Answer 10.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 192
Joined: Tue Apr 29, 2008 7:41 am
Thanked: 14 times

by aatech » Wed May 28, 2008 8:21 am
Unfortunately, I am not able to follow your method... so can't comment..

I will suggest this would be easier...

a = 2+4+6.... +20
b= 1+3+5+....+19

a-b = (2+4+6.... +20)-(1+3+5+....+19) = 1+1+1.. (10 ones) = 10

You can also using Arithmetic Progression formula...
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 231
Joined: Mon Jan 07, 2008 9:39 amFollowed by: 1 member
Thanked: 4 times

by khurram » Wed May 28, 2008 8:52 am
why wont the short cut work

(largest +smallest)/2 for both sequences, to get avg of the sequence

largest -smallest +1 to get number of terms

times the two, avg times the number of terms to get the sum

eg
1, 2,3,4,5
1+5=6/2=3
3*5=15 same as 1+2+3+4+5=15

number of terms= 5-1+1=5.



Thanks
Khurram
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 231
Joined: Mon Jan 07, 2008 9:39 amFollowed by: 1 member
Thanked: 4 times

by khurram » Wed May 28, 2008 8:55 am
aatech
I like your thinking also. diff between each term is 1. so in toal 10 diff between the two.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 231
Joined: Mon Jan 07, 2008 9:39 amFollowed by: 1 member
Thanked: 4 times

by khurram » Wed May 28, 2008 8:58 am
got it

was thinking consecutive not even set and odd set

thanks
khurram so my method cannot be used as that is for consecutive set only
Top
Join the discussion
Senior | Next Rank: 100 Posts
Posts: 58
Joined: Fri Apr 04, 2008 12:36 pm
Thanked: 4 times
GMAT Score:680

by mim3 » Thu May 29, 2008 2:41 pm
khurram wrote:got it

was thinking consecutive not even set and odd set

thanks
khurram so my method cannot be used as that is for consecutive set only
No, the shortcut can still be used as it's still a consecutive set:

sum of set= median x number of terms

2-20(e):
median= (20+2)/2 = 11
# terms= 10
sum= 110

1-19(o):
median= (19+1)/2= 10
# terms= 10
sum= 100

110-100= 10.
Top
Join the discussion