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

It is currently 20 Aug 2019, 07:57

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 average (arithmetic mean) of 6 numbers is 8.5. When one

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 57152
The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 07 Feb 2014, 05:48
5
5
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

91% (01:08) correct 9% (01:34) wrong based on 628 sessions

HideShow timer Statistics

The Official Guide For GMAT® Quantitative Review, 2ND Edition

The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number?

(A) 7.8
(B) 9.8
(C) 10.0
(D) 12.4
(E) 15.0

Problem Solving
Question: 84
Category: Arithmetic Statistics
Page: 72
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
1. Please provide your solutions to the questions;
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!

_________________
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 57152
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 07 Feb 2014, 05:48
2
3
SOLUTION

The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number?

(A) 7.8
(B) 9.8
(C) 10.0
(D) 12.4
(E) 15.0

The average of 6 numbers is 8.5 --> the sum of 6 numbers = (mean)*(number of terms) = 8.5*6 = 51.

The average of 5 numbers is 7.2 --> the sum of 5 numbers = (mean)*(number of terms) = 7.2*5 = 36.

The discarded number = 51 - 36 = 15.

Answer: E.
_________________
General Discussion
Director
Director
User avatar
Joined: 25 Apr 2012
Posts: 668
Location: India
GPA: 3.21
WE: Business Development (Other)
Reviews Badge
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 07 Feb 2014, 11:10
1
The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2 .What is the discarded number?


Sol: Since avg is given for 6 nos, we can find the sum total which is 8.5*6= 51

New average after removal of one number is 7.2 so sum total of 5 nos is 36

Discarded number is 51-36=15

Ans E

Posted from my mobile device
_________________

“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”
Manager
Manager
avatar
B
Joined: 13 Feb 2011
Posts: 81
GMAT ToolKit User
The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 21 Feb 2016, 12:48
1
1
Let's assume every number was 8.5 in the original set, now in order to reduce average to 7.2 by removing just one number, 1.3 \((8.5-7.2=1.3)\) needs to be subtracted from remaining 5 numbers \((1.3*5=6.5)\) along with removing one of the original numbers, i.e. \(6.5+8.5=15.0\)
Answer: E
Manager
Manager
User avatar
Joined: 11 Jan 2014
Posts: 86
Concentration: Finance, Statistics
GMAT Date: 03-04-2014
GPA: 3.77
WE: Analyst (Retail Banking)
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 07 Feb 2014, 13:06
1
Given that the average of 6 numbers is 8.5, then the sum of these numbers is 6*8.5= 51.

Let 'x' be the number removed, (51-x)/5 = 7.2. Solving for x, we get x = 15, so (E).
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2604
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 09 Dec 2016, 02:19
Board of Directors
User avatar
D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4573
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 10 Dec 2016, 01:32
Bunuel wrote:
The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number?

(A) 7.8
(B) 9.8
(C) 10.0
(D) 12.4
(E) 15.0


\(8.5*6 - x = 7.2*5\)

Or, \(51 - x = 36\)

Or, \(x = 15\)

Hence, answer will be (E) 15

_________________
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 )
Senior Manager
Senior Manager
User avatar
S
Joined: 24 Oct 2016
Posts: 254
Location: India
Concentration: Finance, International Business
Schools: IIMB
GMAT 1: 550 Q42 V28
GPA: 3.96
WE: Human Resources (Retail Banking)
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 10 Mar 2017, 23:41
this can be solved very easily from the following method
N-7.2/6 +7.2=8.5 so the new no. will be after solving for N=15
so the answer is E
after knowing the S.D. very precisely we gonna solve these questions within 30 sec.
Board of Directors
User avatar
D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4573
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 11 Mar 2017, 00:16
Bunuel wrote:
The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number?

(A) 7.8
(B) 9.8
(C) 10.0
(D) 12.4
(E) 15.0


\(8.5*6 - X = 7.2*5\)

\(51 - x = 36\)

Or, \(x = 15\)

Thus, the discarded number will be (E) 15.00
_________________
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 )
CEO
CEO
User avatar
V
Joined: 12 Sep 2015
Posts: 3910
Location: Canada
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 17 Dec 2017, 10:02
Top Contributor
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

The average (arithmetic mean) of 6 numbers is 8.5. When one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number?

(A) 7.8
(B) 9.8
(C) 10.0
(D) 12.4
(E) 15.0


Average of 6 numbers = (sum of all 6 numbers)/6
We get: 8.5 = (sum of all 6 numbers)/6
So, sum of the 6 numbers = (6)(8.5)
= 51

When one number is discarded, the average of the remaining numbers becomes 7.2
Sum of remaining 5 numbers = (5)(7.2)
= 36

Discarded number = (sum of original 6 numbers) - (sum of remaining 5 numbers)
= 51 - 36
= 15
= E

RELATED VIDEO FROM OUR COURSE

_________________
Test confidently with gmatprepnow.com
Image
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 12044
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one  [#permalink]

Show Tags

New post 23 Jul 2019, 01:28
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: The average (arithmetic mean) of 6 numbers is 8.5. When one   [#permalink] 23 Jul 2019, 01:28
Display posts from previous: Sort by

The average (arithmetic mean) of 6 numbers is 8.5. When one

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





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