NEW HERE? LEARN MORE
closeclose
Last visit was: 25 Apr 2024, 16:32 It is currently 25 Apr 2024, 16:32
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A certain list consists of 21 different numbers. If n is in

User avatar
udaymathapati
Manager
Manager
Joined: 06 Apr 2010
Posts: 93
Own Kudos [?]: 4922 [2]
Given Kudos: 15
Send PM
Reviews Badge
A certain list consists of 21 different numbers. If n is in [#permalink] New post   Updated on: 25 Aug 2013, 09:36
1
Kudos
1
Bookmarks
00:00
A
B
C
D
E

Difficulty:

65% (hard)

Question Stats:

57% (02:08) correct 43% (02:14) wrong based on 58 sessions
Hide Show timer Statistics
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-certain-list-consists-of-21-different-numbers-if-n-is-in-103995.html

Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
ShowHide Answer
Official Answer
B

Originally posted by udaymathapati on 30 Aug 2010, 10:29.
Last edited by Bunuel on 25 Aug 2013, 09:36, edited 1 time in total.
Edited the answer choices.
User avatar
anshumishra
Manager
Manager
Joined: 25 Jun 2010
Posts: 57
Own Kudos [?]: 136 [0]
Given Kudos: 0
Send PM
GMAT ToolKit User
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   30 Aug 2010, 11:15
Looks like the answer is wrong.

series : a1, a2....a20,n
sum of a1+a2+...+a20 = 20*x (x = average)
so, n = 4*x
Hence, a1+a2+..+a20+n = 24x
So, the fraction asked = 4x/24x = 1/6
User avatar
ezhilkumarank
Senior Manager
Senior Manager
Joined: 24 Jun 2010
Status:Time to step up the tempo
Posts: 273
Own Kudos [?]: 673 [0]
Given Kudos: 50
Location: Milky way
Concentration: International Business, Marketing
Schools:ISB, Tepper - CMU, Chicago Booth, LSB
Send PM
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   30 Aug 2010, 22:15
I also got the same answer - 1/6.

Given n = 4[(Sum of 21 elements - n)/20]

=> n = (Sum of 21 elements - n)/5
=> 5n = (Sum of 21 elements - n)
=> 6n = Sum of 21 elements.

Therefore n/(Sum of 21 elements) => n/6n

Answer should be 1/6.

@ udaymathapati -- Please confirm
User avatar
seekmba
Director
Director
Joined: 17 Feb 2010
Posts: 634
Own Kudos [?]: 3224 [0]
Given Kudos: 6
Send PM
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   09 Sep 2010, 09:04
i got 1/6 too. the options does not seem to blend with the question.
User avatar
vwjetty
Retired Moderator
Joined: 25 Apr 2010
Status:battlecruiser, operational...
Posts: 897
Own Kudos [?]: 518 [0]
Given Kudos: 71
Schools: Carey '16
Send PM
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   09 Sep 2010, 09:59
yeah 1/6th is right i think.
User avatar
AtifS
Manager
Manager
Joined: 20 Jan 2010
Status:Not afraid of failures, disappointments, and falls.
Posts: 217
Own Kudos [?]: 447 [0]
Given Kudos: 260
Concentration: Technology, Entrepreneurship
Schools: Haas '19 Darden '19 INSEAD Jan '19 Stanford '19 Anderson '19 HBS '19
WE:Operations (Telecommunications)
Send PM
GMAT ToolKit User
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   11 Oct 2010, 07:20
I was confused here, as none of the options was a fraction (p/q) but after going through replies, it was confirmed that this question's answer choices need to be verified.
1/6 for me too.
User avatar
B
PiyushK
Director
Director
Joined: 22 Mar 2013
Status:Everyone is a leader. Just stop listening to others.
Posts: 611
Own Kudos [?]: 4595 [0]
Given Kudos: 235
Location: India
GPA: 3.51
WE:Information Technology (Computer Software)
Send PM
Reviews Badge
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   25 Aug 2013, 08:53
Yes 1/6.

n = 4 x (Sum of 20) / 20 = (Sum of 20)/5

(Sum of 21) = (Sum of 20) + n
= (Sum of 20) + (Sum of 20)/5
= 6 x ( Sum of 20 ) / 5

n/(Sum of 21) = ((Sum of 20)/5) / 6 x ( Sum of 20 ) / 5 = 1/6
User avatar
ygdrasil24
Manager
Manager
Joined: 07 Apr 2012
Posts: 71
Own Kudos [?]: 25 [0]
Given Kudos: 45
Location: United States
Concentration: Entrepreneurship, Operations
Schools: ISB '15
GMAT 1: 590 Q48 V23
GPA: 3.9
WE:Operations (Manufacturing)
Send PM
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   25 Aug 2013, 09:15
Wasted time in searching answer in options, sitter problem :\
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92915
Own Kudos [?]: 619022 [1]
Given Kudos: 81595
Send PM
CAT Tests Forum Quiz Mode
Re: A certain list consists of 21 different numbers. If n is in [#permalink] New post   25 Aug 2013, 09:37
1
Kudos
Expert Reply
A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

(A) 1/20
(B) 1/6
(C) 1/5
(D) 4/21
(E) 5/21

Given: \(average_{20}=\frac{sum_{20}}{20}=\frac{n}{4}\) --> \(sum_{20}=5n\) --> \(sum_{21}=sum_{20}+n=5n+n=6n\);

Question: \(n\) is what fraction of the sum of the 21 numbers in the list?
\(\frac{n}{sum_{21}}=\frac{n}{6n}=\frac{1}{6}\).

Answer: B.

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-certain-list-consists-of-21-different-numbers-if-n-is-in-103995.html

Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: A certain list consists of 21 different numbers. If n is in [#permalink]
25 Aug 2013, 09:37
Moderators:
Bunuel
Math Expert
92915 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions