Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 04 May 2016, 12:59

### 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

# PS - combination

Author Message
Manager
Joined: 27 May 2008
Posts: 203
Followers: 1

Kudos [?]: 30 [0], given: 0

### Show Tags

16 Mar 2009, 06:44
00:00

Difficulty:

(N/A)

Question Stats:

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

### HideShow timer Statictics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A group contains 7 boys and some girls. The number of teams of 5 comprising 3 boys and 2 girls is 525. How many girls are in the group?

5
6
7
9
11
CEO
Joined: 17 Nov 2007
Posts: 3580
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 474

Kudos [?]: 2711 [0], given: 359

### Show Tags

16 Mar 2009, 11:44
Expert's post
B
$$525 = C^7_3 * C^x_2=\frac{7*6*5}{3*2}*\frac{x*(x-1)}{2}$$

x(x-1)=30 ---> x=6
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

Manager
Joined: 19 Aug 2006
Posts: 248
Followers: 2

Kudos [?]: 9 [0], given: 0

### Show Tags

16 Mar 2009, 13:10
selvae wrote:
A group contains 7 boys and some girls. The number of teams of 5 comprising 3 boys and 2 girls is 525. How many girls are in the group?

5
6
7
9
11

boys=> 7!/4!3!=35
525=35*g, where g is the number of teams comprising of girls only, so g=525/35=15 girls
We know that 15 = g!/(g-2)!2! , where g is the total number of girls available.

Solving backwards, and plugging the 1st available answer 5 quickly shows us that the number of girls should be a bit higher. Trying the number 6 works: 6!/4!2!=15

Re: PS - combination   [#permalink] 16 Mar 2009, 13:10
Display posts from previous: Sort by