GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 20 Apr 2019, 19:33

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.

Close

Request Expert Reply

Confirm Cancel

The sum of all consecutive odd integers from −21 to 31, inclusive, is

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Retired Moderator
avatar
Joined: 29 Apr 2015
Posts: 838
Location: Switzerland
Concentration: Economics, Finance
Schools: LBS MIF '19
WE: Asset Management (Investment Banking)
GMAT ToolKit User
The sum of all consecutive odd integers from −21 to 31, inclusive, is  [#permalink]

Show Tags

New post 27 Jun 2015, 03:32
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

77% (01:29) correct 23% (02:07) wrong based on 163 sessions

HideShow timer Statistics

The sum of all consecutive odd integers from −21 to 31, inclusive, is

A. 130
B. 135
C. 150
D. 156
E. 235


The sum of odd integers from -21 to 21 is zero because each negative value cancels out its positive counterpart. Based on this, add odd integers from 22 to 31 to get the sum of consecutive integers from -21 to 31.

23 + 25 + 27 + 29 + 31 = 135.

_________________
Saving was yesterday, heat up the gmatclub.forum's sentiment by spending KUDOS!

PS Please send me PM if I do not respond to your question within 24 hours.
Most Helpful Expert Reply
CEO
CEO
User avatar
D
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2906
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
Reviews Badge
Re: The sum of all consecutive odd integers from −21 to 31, inclusive, is  [#permalink]

Show Tags

New post 27 Jun 2015, 03:55
3
2
reto wrote:
The sum of all consecutive odd integers from −21 to 31, inclusive, is

A. 130
B. 135
C. 150
D. 156
E. 235




The sum of odd integers from -21 to 21 = - 21 - 19 - 17 ---------+17 + 19 + 21 + 23 + 25 + 27 + 29 + 31

The sum of odd integers from -21 to 21 = 0 + 5* 27 = 0 + 135 = 135

When the terms are separated by a constant amount then Mean = media = Average of first and last term

Sum of 23 + 25 + 27 + 29 + 31 = 27(mean) * 5(no. of terms) = 135


Answer: Option B
_________________
Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION
General Discussion
Intern
Intern
avatar
Joined: 28 Dec 2015
Posts: 39
Re: The sum of all consecutive odd integers from −21 to 31, inclusive, is  [#permalink]

Show Tags

New post 30 Jun 2016, 22:06
-21 to +21=sum=0
Now add the rest of them
23+25+27+29+31=135
Intern
Intern
avatar
B
Joined: 08 Jun 2015
Posts: 20
Location: United States
Concentration: Finance, Economics
WE: Engineering (Other)
Re: The sum of all consecutive odd integers from −21 to 31, inclusive, is  [#permalink]

Show Tags

New post 19 Aug 2017, 05:14
By using the formulas of AP Last term = First Term + (Number of terms - 1 ) X Difference, 31 = -21 + (n-1) X 2 ==> we get Number of terms = 27.
and by Sum of AP = n/2 X (First term + last term ), S = 27/2 X (-21+31) ==> we get Sum = 135.
Intern
Intern
avatar
Joined: 12 May 2016
Posts: 4
Re: The sum of all consecutive odd integers from −21 to 31, inclusive, is  [#permalink]

Show Tags

New post 19 Aug 2017, 06:18
The answer is B. From -21 to +21 is zero. Then, 23+25+27+29+31=135.

Sent from my General Mobile 4G Dual using GMAT Club Forum mobile app
GMAT Club Bot
Re: The sum of all consecutive odd integers from −21 to 31, inclusive, is   [#permalink] 19 Aug 2017, 06:18
Display posts from previous: Sort by

The sum of all consecutive odd integers from −21 to 31, inclusive, is

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.