Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 23 May 2017, 22:38

### 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

# Combination problem

 post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Intern
Joined: 20 Apr 2006
Posts: 39
Followers: 0

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

### Show Tags

18 Jul 2006, 07:28
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Can anyone please answer and explain the following question -

Thanks

--
To furnish a room in a model house, an interior decorator is to select 2 chairs and 2 tables from a collection of chairs and tables in a warehouse that are all different from each other. If there are 5 chairs in the warehouse and if 150 different combinations are possible, how mnay tables are in the warehouse?
[/b]
Intern
Joined: 18 Apr 2006
Posts: 36
Followers: 0

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

### Show Tags

18 Jul 2006, 08:14
150 = 5C2 * nC2

Solving this we get n=6 hence 6 tables.
Manager
Joined: 14 Mar 2006
Posts: 208
Followers: 2

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

### Show Tags

18 Jul 2006, 08:52
I did it by trial n error and got 6 tables.

6C2.
Senior Manager
Joined: 22 May 2006
Posts: 369
Location: Rancho Palos Verdes
Followers: 1

Kudos [?]: 122 [0], given: 0

### Show Tags

18 Jul 2006, 19:10
total possible combination = 150

from selecting chiars 5C2
from selecting tables XC2

thus 5C2*XC2 = 150

(5*4)/2 * (X*X-1)/2 = 150

X^2-X-30 = 0

X = 6 or -5 (X>0)

so ans is 6
_________________

The only thing that matters is what you believe.

GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5045
Location: Singapore
Followers: 31

Kudos [?]: 376 [0], given: 0

### Show Tags

18 Jul 2006, 19:17
# of ways to pick 2 chairs = 5C2 = 5!/2!3! = 10 ways

# of ways to pick tables = tC2 = t!/2!(t-2)!

Total number of ways = 150 = 10 * t!/(t-2)!2!

15 = t!/2!(t-2)!
30 = t!/(t-2)!
t(t-1) = 30
t^2 -t - 30 = 0

t = 6
SVP
Joined: 30 Mar 2006
Posts: 1730
Followers: 1

Kudos [?]: 82 [0], given: 0

### Show Tags

18 Jul 2006, 23:01
Two chairs can be chosen in 5C2 ways
Let there be n tables.
Two tables can be chosen in nC2 ways.

Total ways = 5C2*nC2

Given there are 150 ways

5C2*nC2 = 150
10 * nC2 = 150
nC2 = 15

hence n = 6
CEO
Joined: 20 Nov 2005
Posts: 2898
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Followers: 25

Kudos [?]: 288 [0], given: 0

### Show Tags

18 Jul 2006, 23:12
5C2 * xC2 = 150

10 * x * (x-1)/2 = 150
x*(x-1) = 30
x^2-x-30= 0
(x-6)(x-5) = 0
Therefore x = 6
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

18 Jul 2006, 23:12
Display posts from previous: Sort by

# Combination problem

 post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO 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®.