NEW HERE? LEARN MORE
closeclose
Last visit was: 28 Apr 2024, 15:39 It is currently 28 Apr 2024, 15:39
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

official guide (OG) 11th edition 215

User avatar
evlanderwin
Intern
Intern
Joined: 12 Apr 2009
Posts: 5
Own Kudos [?]: [0]
Given Kudos: 7
Send PM
official guide (OG) 11th edition 215 [#permalink] New post   16 Apr 2009, 08:35
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

33% (00:00) correct 67% (00:51) wrong based on 8 sessions
Hide Show timer Statistics
if m is the average (arithmetic mean) of the first 10 positive multiples of 5 and if M is the median of the first 10 positive multiples of 5, what is the value of M-m?

a. -5
b. 0
c. 5
d. 25
e. 27.5

according to the answer in OG, the first 10 positive multiples are 1,2,3, ...,8,9,10, but i think positive number could also be 1.1, 1.2 .... or some other number which bigger than 0.

the correct answer is e, but why? Thks a lot



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 Quantitative Questions 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!
User avatar
goldeneagle94
Manager
Manager
Joined: 08 Feb 2009
Posts: 77
Own Kudos [?]: 96 [1]
Given Kudos: 3
Concentration: Entrepreneurship
Schools:Anderson
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   16 Apr 2009, 09:22
1
Kudos
"MULTIPLE" by definition has to be resulted when multiplied by a an Integer.
For example, 10 is a multiple of 5 because when 5 is multiplied by 2, it results in 10.
In the same way, 5 x 1.5 = 7.5 doesn't imply that 7.5 is a multiple of 5 because 1.5 is not an integer.

The answer,

First 10 positive multiples of 5 are = 5,10,15,20,25,30,35,40,45,50.
Arithmetic mean would be = 5(1+2+3......9+10)/10 = 27.5

In the same way, Median = (25+30)/2 = 27.5

Thus, M-m = 0.


Official Answer as listed in OG 11 is B.

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
User avatar
evlanderwin
Intern
Intern
Joined: 12 Apr 2009
Posts: 5
Own Kudos [?]: [0]
Given Kudos: 7
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   20 Apr 2009, 07:57
Goldenagle94,

catch your point.
thks a lot:)
User avatar
bandit
Manager
Manager
Joined: 22 Feb 2009
Posts: 94
Own Kudos [?]: 239 [5]
Given Kudos: 10
Concentration: Biotech MC
Schools:Kellogg (R1 Dinged),Cornell (R2), Emory(Interview Scheduled), IESE (R1 Interviewed), ISB (Interviewed), LBS (R2), Vanderbilt (R3 Interviewed)
 Q49  V38
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   20 Apr 2009, 09:42
5
Kudos
Here one important rule to remember is that, for equally spaced numbers median=mean. Therefore, mean-median=0. we dont need to solve it.
User avatar
evlanderwin
Intern
Intern
Joined: 12 Apr 2009
Posts: 5
Own Kudos [?]: [0]
Given Kudos: 7
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   21 Apr 2009, 07:17
bandit wrote:
Here one important rule to remember is that, for equally spaced numbers median=mean. Therefore, mean-median=0. we dont need to solve it.


thks. :-D
User avatar
kbulse
Manager
Manager
Joined: 01 Jan 2008
Posts: 139
Own Kudos [?]: 111 [0]
Given Kudos: 2
Concentration: Finance, entrepreneurship
Schools:Booth, Stern, Haas
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   21 Apr 2009, 07:45
bandit wrote:
Here one important rule to remember is that, for equally spaced numbers median=mean. Therefore, mean-median=0. we dont need to solve it.

what does "equally spaced" mean?
User avatar
bandit
Manager
Manager
Joined: 22 Feb 2009
Posts: 94
Own Kudos [?]: 239 [1]
Given Kudos: 10
Concentration: Biotech MC
Schools:Kellogg (R1 Dinged),Cornell (R2), Emory(Interview Scheduled), IESE (R1 Interviewed), ISB (Interviewed), LBS (R2), Vanderbilt (R3 Interviewed)
 Q49  V38
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   22 Apr 2009, 00:52
1
Kudos
kbulse wrote:
bandit wrote:
Here one important rule to remember is that, for equally spaced numbers median=mean. Therefore, mean-median=0. we dont need to solve it.

what does "equally spaced" mean?


For numbers in arithmatic progression (AP). For example

1,2,3,4,5,6
5,10,15,20,25
3,6,9,12
User avatar
ALD
Manager
Manager
Joined: 15 Apr 2008
Posts: 90
Own Kudos [?]: 21 [0]
Given Kudos: 1
Send PM
Re: official guide (OG) 11th edition 215 [#permalink] New post   23 Apr 2009, 14:40
smart tip by goldeneagle and bandit



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: official guide (OG) 11th edition 215 [#permalink]
23 Apr 2009, 14:40
Moderators:
Bunuel
Math Expert
92977 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