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

It is currently 13 Dec 2018, 13:23

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
Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • GMATbuster's Weekly GMAT Quant Quiz, Tomorrow, Saturday at 9 AM PST

     December 14, 2018

     December 14, 2018

     09:00 AM PST

     10:00 AM PST

    10 Questions will be posted on the forum and we will post a reply in this Topic with a link to each question. There are prizes for the winners.
  • The winning strategy for 700+ on the GMAT

     December 13, 2018

     December 13, 2018

     08:00 AM PST

     09:00 AM PST

    What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.

There are 9 consecutive integers in a certain sequence. If the average

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

Hide Tags

Manager
Manager
avatar
B
Joined: 03 Feb 2017
Posts: 75
Location: Australia
GMAT 1: 720 Q48 V40
There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Jun 2017, 04:23
1
8
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

76% (02:04) correct 24% (02:09) wrong based on 145 sessions

HideShow timer Statistics

There are 9 consecutive integers in a certain sequence. If the average of the first seven integers in the sequence is n, what is the average of all 9 integers in the sequence?

A) n
B) n-1
C) n+1
D) 2n
E) n(n+1)
Senior PS Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3325
Location: India
GPA: 3.12
Premium Member CAT Tests
Re: There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Jun 2017, 05:09
1
Consider the 9 consecutive number 1,2,3,4,5,6,7,8,9

The average of the first seven integers is 4(Middle term, since elements are in AP)
The average of the entire lot will be 5(which is n+1, provided the average of first 7 numbers is n)

Hence, Option C is the answer option.
_________________

You've got what it takes, but it will take everything you've got

CEO
CEO
User avatar
D
Joined: 11 Sep 2015
Posts: 3237
Location: Canada
Re: There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Jun 2017, 05:47
Top Contributor
1
danlew wrote:
There are 9 consecutive integers in a certain sequence. If the average of the first seven integers in the sequence is n, what is the average of all 9 integers in the sequence?

A) n
B) n-1
C) n+1
D) 2n
E) n(n+1)


USEFUL RULE: In a set of EQUALLY SPACED numbers, the mean of the set equals the median of the set

Let O, O, O, O, O, O, O, O, O represent the 9 consecutive integers listed in ascending order.

The average (aka MEAN) of the first seven integers in the sequence is n
Here are the first seven integers: O, O, O, O, O, O, O
Since consecutive integers are equally spaced, the mean = the median
The median of these 7 numbers is the middlemost number.
So, the middlemost value is also the mean.
We get: O, O, O, n, O, O, O
So, our NINE numbers now look like this: O, O, O, n, O, O, O, O, O

What is the average of all 9 integers in the sequence?
Using the same logic, we can see that the mean of the 9 numbers is the middlemost number.
So, replace the middlemost number with a "?" : O, O, O, n, ?, O, O, O, O

We can see that ? (the mean of all 9 integers) is 1 GREATER THAN n (the mean of the first 7 integers)
In other words, the mean of all 9 integers = n+1

Answer:

RELATED VIDEO

_________________

Test confidently with gmatprepnow.com
Image

Board of Directors
User avatar
P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4276
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User Premium Member CAT Tests
Re: There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Jun 2017, 08:03
danlew wrote:
There are 9 consecutive integers in a certain sequence. If the average of the first seven integers in the sequence is n, what is the average of all 9 integers in the sequence?

A) n
B) n-1
C) n+1
D) 2n
E) n(n+1)


Plug in and check...

Let the sequence of consecutive integers be 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9

Sum of first 7 numbers is 28
Average of first 7 numbers is \(\frac{28}{7} = 4\)

Sum of first 9 numbers is 45
Average of first 9 numbers is \(\frac{45}{9} = 5\)

Hence, the answer will be (C) n+1
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

VP
VP
avatar
P
Joined: 07 Dec 2014
Posts: 1128
There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Jun 2017, 13:04
danlew wrote:
There are 9 consecutive integers in a certain sequence. If the average of the first seven integers in the sequence is n, what is the average of all 9 integers in the sequence?

A) n
B) n-1
C) n+1
D) 2n
E) n(n+1)


if a=average of all 9 consecutive integers,
a will be the 5th term
n will be the 4th term
a=n+(5-4)=n+1
C
Intern
Intern
avatar
B
Joined: 12 Oct 2017
Posts: 1
There are 9 consecutive integers in a certain sequence. If the average  [#permalink]

Show Tags

New post 16 Dec 2017, 06:55
Since we know n is average for 7, for 9 consecutive numbers it would be n+ (n+1) +(n+2) / 3 = 3n+3/3. which is n+1.
Ans C.
GMAT Club Bot
There are 9 consecutive integers in a certain sequence. If the average &nbs [#permalink] 16 Dec 2017, 06:55
Display posts from previous: Sort by

There are 9 consecutive integers in a certain sequence. If the average

  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®.