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 350,000 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:

There are 9 books on a shelf, 7 hard cover and 2 soft cover. [#permalink]
02 Oct 2003, 07:48

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

There are 9 books on a shelf, 7 hard cover and 2 soft cover. How many different combinations exist in which you choose 4 books from the 9 and have at least one of them be a soft cover book? _________________

C(9,4) = 9!/(4! * 5!) = 126
So, that means...this will look like this:
9*8*7*6*5/4*3*2*5*4*3*2*1...right??
but calculate it.......its not 91 _________________

why don't u try the permutation/combinations stuff on this website.
U can also consult any basic book on combinations/permutations or search on google for some stuff. I guess someone posted in share GMAT expe. section a link to some basic permutation/combo site. Check it out
Remember, u would want to be thorough in this area cause more and more questions based on them have begun to appear on GMAT
also 9! = 1*2*3...*8*9
it's pretty late here... time to sleep...
nowadays even in sleep i get these tormenting SC's...
thanks

Social entrepreneurs aren't running charities : ‘It’s easy to think about it in terms of charity: it’s not. They are sustainable, trading, revenue-generating businesses. The benefit of them...