It is currently 22 Nov 2017, 00:41

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Jill is dividing her ten-person class into two teams of eq

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

### Hide Tags

Manager
Joined: 09 Feb 2013
Posts: 121

Kudos [?]: 1174 [2], given: 17

Jill is dividing her ten-person class into two teams of eq [#permalink]

### Show Tags

28 Feb 2013, 05:25
2
KUDOS
6
This post was
BOOKMARKED
00:00

Difficulty:

95% (hard)

Question Stats:

45% (01:13) correct 55% (01:30) wrong based on 177 sessions

### HideShow timer Statistics

Jill is dividing her ten-person class into two teams of equal size for a basketball game. If no one will sit out, how many different match-ups between the two teams are possible?

A. 10
B. 25
C. 126
D. 252
E. 630
[Reveal] Spoiler: OA

_________________

Kudos will encourage many others, like me.
Good Questions also deserve few KUDOS.

Last edited by Bunuel on 28 Feb 2013, 06:14, edited 1 time in total.
Edited the question.

Kudos [?]: 1174 [2], given: 17

Math Expert
Joined: 02 Sep 2009
Posts: 42302

Kudos [?]: 133002 [2], given: 12402

Re: Jill is dividing her ten-person class into two teams of eq [#permalink]

### Show Tags

28 Feb 2013, 06:29
2
KUDOS
Expert's post
2
This post was
BOOKMARKED
emmak wrote:
Jill is dividing her ten-person class into two teams of equal size for a basketball game. If no one will sit out, how many different match-ups between the two teams are possible?

A. 10
B. 25
C. 126
D. 252
E. 630

There should be 5 people in each group. We can divide a group of 10 people into 2 teams of 5 in $$\frac{C^5_{10}*C^5_5}{2!}=126$$ ways (dividing by 2! because the order of the groups doesn't matter).

For more on this check:
a-group-of-8-friends-want-to-play-doubles-tennis-how-many-55369.html
in-how-many-different-ways-can-a-group-of-9-people-be-85993.html
probability-88685.html
probability-85993.html
combination-55369.html
sub-committee-86346.html

Hope it helps.
_________________

Kudos [?]: 133002 [2], given: 12402

Senior Manager
Joined: 23 Oct 2010
Posts: 381

Kudos [?]: 403 [0], given: 73

Location: Azerbaijan
Concentration: Finance
Schools: HEC '15 (A)
GMAT 1: 690 Q47 V38
Re: Jill is dividing her ten-person class into two teams of eq [#permalink]

### Show Tags

02 Mar 2013, 11:47
here is a formula -http://gmatclub.com/forum/a-group-of-8-friends-want-to-play-doubles-tennis-how-many-55369.html#p689312
The number of ways in which mn different items can be divided equally into m groups, each containing n objects and the order of the groups is not important is -
(mn)!/(n!)^m*m!

10! /((5!)^2*2!) =126
_________________

Happy are those who dream dreams and are ready to pay the price to make them come true

I am still on all gmat forums. msg me if you want to ask me smth

Kudos [?]: 403 [0], given: 73

EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10158

Kudos [?]: 3530 [1], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: Jill is dividing her ten-person class into two teams of eq [#permalink]

### Show Tags

23 Apr 2015, 15:42
1
KUDOS
Expert's post
Hi All,

This question tests your knowledge of the Combination Formula, but it comes with a rare "twist" that most people don't realize. Here's a bit more information on that "twist":

With 10 players, the process of figuring out how many groups of 5 can be formed is pretty straight-forward....

10C5 = 10!/(5!5!) = 256 possible groups of 5

Once forming that first group of 5, the remaining 5 players would all be placed on the second team by default.

The 'twist' is that the two teams of 5 can "show up" in either order:

For example, if we call the two teams of 5 players: A,B,C,D,E and F,G,H,I,J

ABCDE vs. FGHIJ

is the SAME match-up as....

FGHIJ vs. ABCDE

So we are NOT allowed to count that matchup twice. This means we have to divide the 256 by 2.

[Reveal] Spoiler:
C

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

# 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/

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

Kudos [?]: 3530 [1], given: 173

Manager
Joined: 30 Aug 2017
Posts: 72

Kudos [?]: 1 [0], given: 168

Location: Korea, Republic of
GMAT 1: 660 Q51 V26
GPA: 3.68
Re: Jill is dividing her ten-person class into two teams of eq [#permalink]

### Show Tags

04 Oct 2017, 20:14
good question.

When we pick 5 people out of 10 people(10C5), we can make each side of team simultaneously.
And We have to devide by 2 to avoid duplication.

Kudos [?]: 1 [0], given: 168

Re: Jill is dividing her ten-person class into two teams of eq   [#permalink] 04 Oct 2017, 20:14
Display posts from previous: Sort by

# Jill is dividing her ten-person class into two teams of eq

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

 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®.