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

It is currently 21 Apr 2019, 21:15

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

Each shelf of a bookcase contained 12 books. If the librarian took out

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

Hide Tags

 
Manager
Manager
User avatar
Joined: 04 Aug 2013
Posts: 96
Location: India
Schools: McCombs '17
GMAT 1: 670 Q47 V35
GPA: 3
WE: Manufacturing and Production (Pharmaceuticals and Biotech)
Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 24 Sep 2014, 20:01
1
3
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

75% (02:10) correct 25% (02:09) wrong based on 92 sessions

HideShow timer Statistics

Each shelf of a bookcase contained 12 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but the last one contained 8 books and that last shelf contained 11 books, how many shelves does the bookcase have?

A. 5
B. 6
C. 7
D. 8
E. 9

M09-13
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1813
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 24 Sep 2014, 22:07
2
1
Let the total shelf's = x

Books in each shelf = 12

Total Books = 12x .............. (1)

Books removed = 21 ............. (2)

Rearrangement = 8(x-1) + 11 (1) ............... (3)

Setting up the equation (1) = (2) + (3)

12x = 21 + 8x - 8 + 11

4x = 24

x = 6

Answer = B
_________________
Kindly press "+1 Kudos" to appreciate :)
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 54401
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 25 Sep 2014, 02:11
anceer wrote:
Each shelf of a bookcase contained 12 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but the last one contained 8 books and that last shelf contained 11 books, how many shelves does the bookcase have?

A. 5
B. 6
C. 7
D. 8
E. 9

M09-13


Say there are total of \(x\) shelves, then: \(12*x=21+8*(x-1)+11\), which gives \(x=6\).

Answer: B
_________________
Manager
Manager
avatar
Joined: 02 May 2012
Posts: 66
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 17 Dec 2014, 06:09
Although i am able to understand the solution but still not confident if I will be able to solve similar question. Confusion is

" so that all shelves but the last one contained 8 books " -- last shelf has 8 Books ??

But the question says " last shelf contained 11 books "

Is the language wrong , can someone post a better explanation ?
_________________
If you like my post Kudos Please
__________________________________________________
Support ====> http://udaanshimla.ketto.org/campaign/campaign_details.php?fmd_id=757
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 54401
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 17 Dec 2014, 06:24
1
aashu4uiit wrote:
Although i am able to understand the solution but still not confident if I will be able to solve similar question. Confusion is

" so that all shelves but the last one contained 8 books " -- last shelf has 8 Books ??

But the question says " last shelf contained 11 books "

Is the language wrong , can someone post a better explanation ?


All shelves but the last one contained 8 books and that last shelf contained 11 books means that all shelves but the last one contained 8 books, so if there are total of x shelves, then the number of shelves with 8 books is x - 1.

Hope it's clear.
_________________
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 13958
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 21 Dec 2014, 20:02
Hi All,

This question can be solved by TESTing THE ANSWERS.

We know from the prompt that we have a certain number of bookshelves and each shelf contains 12 books. We're then told that a librarian takes away 21 books and we're left with a bunch of shelves with 8 books each and one shelf with 11 books. We're asked for the number of bookshelves.

Here's how you can TEST THE ANSWERS....We just need to find an answer that "fits" with all of the given information...

If there were 5 shelves....
5(12) = 60 total books
Take 21 away = 60 - 21 = 39
Take 11 away = 39 - 11 = 28
Is 28 the sum of a "bunch" of 8s? 8+8+8 = 24, but not 28.
Eliminate Answer A.

If there were 6 shelves...
6(12) = 72 total books
Take 21 away = 72 - 21 = 51
Take 11 away = 51 - 11 = 40
Is 40 the sum of a "bunch" of 8s? 8+8+8+8+8 = 40. YES IT IS.
This MUST be the answer.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/
Director
Director
User avatar
G
Joined: 23 Jan 2013
Posts: 549
Schools: Cambridge'16
Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 21 Dec 2014, 22:15
right equation is:

12x-21=8(x-1)+11
x=6
shelves and books in both sides are equal

wrong equation is:

12x-21=8x+11
x=8
in this case right side has one shelf more
Senior Manager
Senior Manager
User avatar
B
Joined: 28 Jun 2015
Posts: 290
Concentration: Finance
GPA: 3.5
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 16 Jul 2017, 23:00
anceer wrote:
Each shelf of a bookcase contained 12 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but the last one contained 8 books and that last shelf contained 11 books, how many shelves does the bookcase have?

A. 5
B. 6
C. 7
D. 8
E. 9

M09-13


Let the number of shelves be \(x\). So, total number of books = \(12x\).

Removing \(21\) books would leave \((12x-21)\) books to be rearranged.

Last \(2\) shelves would contain \((11+8) = 19\) books, that would leave \((12x-21-19) = (12x-40)\) books to be re-arranged into \((x-2)\) shelves equally.

\(\frac{12x-40}{x-2} = n\) (\(n\) must be an integer)

A. \(5\)
\(\frac{12(5) - 40}{5-2} = \frac{20}{3}\) - not an integer.

B. \(6\)
\(\frac{12(6) - 40}{6-2} = \frac{32}{4} = 8\). YES.

C. \(7\)
\(\frac{12(7) - 40}{7-2} = \frac{44}{5}\) - not an integer.

D. \(8\)
\(\frac{12(8) - 40}{8-2} = \frac{56}{6}\) - not an integer.

E. \(9\)
\(\frac{12(9) - 40}{9-2} = \frac{68}{7}\) - not an integer.

So, the ans is B.
_________________
I used to think the brain was the most important organ. Then I thought, look what’s telling me that.
Manager
Manager
avatar
G
Joined: 27 Jan 2016
Posts: 134
Schools: ISB '18
GMAT 1: 700 Q50 V34
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 16 Jul 2017, 23:14
12x -21 = 8(x-1)+11
X=6

Sent from my Lenovo A7010a48 using GMAT Club Forum mobile app
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 10578
Re: Each shelf of a bookcase contained 12 books. If the librarian took out  [#permalink]

Show Tags

New post 14 Apr 2019, 05:54
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: Each shelf of a bookcase contained 12 books. If the librarian took out   [#permalink] 14 Apr 2019, 05:54
Display posts from previous: Sort by

Each shelf of a bookcase contained 12 books. If the librarian took out

  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®.