It is currently 21 Jan 2018, 10:55

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A group of students, each of whom has prepared a presentation, is

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

Hide Tags

Director
Director
User avatar
B
Status: I don't stop when I'm Tired,I stop when I'm done
Joined: 11 May 2014
Posts: 563

Kudos [?]: 3293 [0], given: 220

Location: Bangladesh
Concentration: Finance, Leadership
GPA: 2.81
WE: Business Development (Real Estate)
A group of students, each of whom has prepared a presentation, is [#permalink]

Show Tags

New post 05 Jun 2016, 13:32
4
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

57% (00:59) correct 43% (00:56) wrong based on 284 sessions

HideShow timer Statistics

A group of students, each of whom has prepared a presentation, is asked to choose who will give presentations during the next class meeting and in what order they will be given. How many different ways are there to select and arrange the order of presentations?

(1) Five students must be chosen.

(2) All but three students must give presentations at the next class meeting.
[Reveal] Spoiler: OA

_________________

Md. Abdur Rakib

Please Press +1 Kudos,If it helps
Sentence Correction-Collection of Ron Purewal's "elliptical construction/analogies" for SC Challenges

Kudos [?]: 3293 [0], given: 220

Expert Post
5 KUDOS received
Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4647

Kudos [?]: 9298 [5], given: 117

Re: A group of students, each of whom has prepared a presentation, is [#permalink]

Show Tags

New post 06 Jun 2016, 10:43
5
This post received
KUDOS
Expert's post
4
This post was
BOOKMARKED
AbdurRakib wrote:
A group of students, each of whom has prepared a presentation, is asked to choose who will give presentations during the next class meeting and in what order they will be given. How many different ways are there to select and arrange the order of presentations?

(1) Five students must be chosen.

(2) All but three students must give presentations at the next class meeting.

Dear AbdurRakib,
I'm happy to respond. :-) This is a good question.

Statement #1: Five students must be chosen
Here, we don't know the pool. If there are only five students total, then there is only one group of individuals, and it is simply a matter of arranging them. If there are 100 students, then there would be a mindbogglingly large number of combinations of the five people that could be picked (you know have to know how to calculate this, but it's actually over seventy-five million!!) The number depends in part on the size of the pool. This statement, alone and by itself, is insufficient.

Now, we have to be very careful to blot the first statement from our minds and consider statement #2 in its pristine solitude.

Statement #2: All but three students must give presentations at the next class meeting.
Now, we know the number of "not chosens," but we have no idea how many are chosen. It could be that there are four students total, and one gives the presentation in the next class: this would result in simply four ways of choosing. Or there could be six students, and three give it next class: for this, even with out a calculation, we can see that there would be more than four ways of choosing. Without knowing definitely the number chosen, we cannot answer the prompt question. This statement, alone and by itself, is insufficient.

Now, consider the two statement together.
Now, five are chosen for next class, and 3 remain unchosen, so the total number of students with presentations is 8. How many combinations of 5 students can we pick from the 8? That's 8C5. Once, we have those five, we can put them in 5! orders. Thus, the total number of ways is
N = (8C5)(5!)
We don't need to calculate. It's enough to know that we could. Together, both statements are sufficient.
OA = (C)

For those curious about the calculation:
8C5 = 56
5! = 120

N = (8C5)(5!) = (56)(120) = 56(100 + 20) = 5600 + 1120 = 6720

Mike :-)
_________________

Mike McGarry
Magoosh Test Prep

Image

Image

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Kudos [?]: 9298 [5], given: 117

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 14201

Kudos [?]: 291 [0], given: 0

Premium Member
Re: A group of students, each of whom has prepared a presentation, is [#permalink]

Show Tags

New post 19 Nov 2017, 07:55
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 291 [0], given: 0

Re: A group of students, each of whom has prepared a presentation, is   [#permalink] 19 Nov 2017, 07:55
Display posts from previous: Sort by

A group of students, each of whom has prepared a presentation, is

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


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.