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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

70% (01:20) correct 30% (01:26) wrong based on 100 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?

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

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

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

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

Answer: B

Hi Bunuel,

Thanks for the explanation. However, why do you subtract "1" from 8*(x-1)? Can you please verify?

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

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

Answer: B

Hi Bunuel,

Thanks for the explanation. However, why do you subtract "1" from 8*(x-1)? Can you please verify?

Thank you so much. Aram

We are told that all shelves but the last one contained 8 books, so the number of shelves with 8 books is x - 1.
_________________

What if we plug in values? For example we have 6 shelves, thus 6*12=72 books - remove 21 books=51-11 books=40/8=5 shelves left+1 with 11 books=6 justify and 8 shelves, 8*12=96-21=75-11=64/8=8 shelves with 8 books + 1 shelf with 11 books=9 thus 8 doesn't equal 9. So we have only 6 is the correct choice.

Could someone please help explain to me why the following equation would not work for this problem? I got 8, which is the wrong answer, but am trying to figure out where my thought process crapped out on me. Thanks for your help.

12 books per shelf minus 21 books = 8 books per shelf + 11 on the last shelf 12x - 21 = 8x + 11 x = 8

Are the 21 books removed from equation all together?

Could someone please help explain to me why the following equation would not work for this problem? I got 8, which is the wrong answer, but am trying to figure out where my thought process crapped out on me. Thanks for your help.

12 books per shelf minus 21 books = 8 books per shelf + 11 on the last shelf 12x - 21 = 8x + 11 x = 8

Are the 21 books removed from equation all together?

Could someone please help explain to me why the following equation would not work for this problem? I got 8, which is the wrong answer, but am trying to figure out where my thought process crapped out on me. Thanks for your help.

12 books per shelf minus 21 books = 8 books per shelf + 11 on the last shelf 12x - 21 = 8x + 11 x = 8

Are the 21 books removed from equation all together?

The problem in highlighted part. You missed that All but one. So it should be 8(x -1). What you did is that you multiplied by 8x and add another self with 11.