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

It is currently 21 Oct 2019, 08:29

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) cost per book for the 12 books on a cert

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

Hide Tags

Find Similar Topics 
Intern
Intern
User avatar
Joined: 07 Sep 2016
Posts: 20
Location: Brazil
Concentration: Sustainability, International Business
Schools: Rotman '19 (S)
GMAT 1: 590 Q43 V28
GPA: 2.95
WE: Account Management (Commercial Banking)
The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 28 Sep 2016, 13:30
11
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

67% (01:33) correct 33% (01:51) wrong based on 360 sessions

HideShow timer Statistics

The average (arithmetic mean) cost per book for the 12 books on a certain table is k dollars. If a book that costs 18 dollars is removed from the table and replaced by a book that costs 42 dollars, then in terms of k, what will be the average cost per book, in dollars, for the books in the table?

A) k+2

B) k - 2

C) 12+ 24/k

D) 12- 24/k

E) 12k-6
Most Helpful Community Reply
Manager
Manager
avatar
Joined: 05 Jun 2015
Posts: 77
Location: United States
WE: Engineering (Transportation)
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 28 Sep 2016, 18:39
4
3
\(Average = \frac{Total Cost}{number of books}\)
Let S be the sum of costs of all the books.
\(K = \frac{S}{12}\)

One book costing 18 is replaced with one costing 42.
Sum of costs = (S-18) + 42 = S+24

Average = \(\frac{(S+24)}{12}\)
= \(\frac{S}{12}\) +2
= \(K+2\)
General Discussion
Board of Directors
User avatar
D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4776
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 29 Sep 2016, 11:17
2
Coruja wrote:
The average (arithmetic mean) cost per book for the 12 books on a certain table is k dollars. If a book that costs 18 dollars is removed from the table and replaced by a book that costs 42 dollars, then in terms of k, what will be the average cost per book, in dollars, for the books in the table?

A) k+2

B) k - 2

C) 12+ 24/k

D) 12- 24/k

E) 12k-6


Quote:
he average (arithmetic mean) cost per book for the 12 books on a certain table is k dollars.


Total cost of 12 books = 12k

Quote:
If a book that costs 18 dollars is removed from the table and replaced by a book that costs 42 dollars


Total cost of books now = 12k - 18 + 42 Or, 12k +24

Quote:
what will be the average cost per book, in dollars, for the books in the table


Average cost will be \(\frac{(12k + 24 )}{24}\) = k + 2

Hence answer will be (A) k + 2

_________________
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 )
Current Student
User avatar
B
Status: DONE!
Joined: 05 Sep 2016
Posts: 357
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 15 Oct 2016, 09:18
2
Logically, if we replace a book that was $18 with a book that was $42 --> the difference between the two is 24; this number is "absorbed" by the total number of books (i.e. 12), so each book's average goes up by 2
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2563
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 15 Dec 2016, 14:39
2
Great Official Question.
Here is my solution to this one=>
Mean (12)=k

\(Mean = \frac{Sum}{#}\)

Hence Sum(12)=12k

Now new Sum(12)=12k-18+42=12k+24

New mean =\(\frac{12k+24}{12}=k+2\)

Hence A

_________________
Director
Director
User avatar
S
Status: Come! Fall in Love with Learning!
Joined: 05 Jan 2017
Posts: 531
Location: India
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 27 Feb 2017, 04:29
Total cost = 12k
After replacement the total cost will be 12k -18 +42 = 12k +24
Average cost is (12k +24)/12 = k+2. Option A
_________________
GMAT Mentors
Image
Senior Manager
Senior Manager
User avatar
S
Joined: 24 Oct 2016
Posts: 251
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) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 27 Feb 2017, 06:48
1
we can see the book that has replaced cost more (42) and so we can calculate the diff which ultimately increased the avg cost of the books.
so 42-18=24 can be equally divided among 12 books that would be +2 and now as we know the previous avg that k so new avg=old avg(k)+(2)addition in each books cost =k+2
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13367
Re: The average (arithmetic mean) cost per book for the 12 books on a cert  [#permalink]

Show Tags

New post 16 Oct 2018, 17:07
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) cost per book for the 12 books on a cert   [#permalink] 16 Oct 2018, 17:07
Display posts from previous: Sort by

The average (arithmetic mean) cost per book for the 12 books on a cert

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





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