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

 It is currently 04 May 2015, 06:47

### 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: Combinatorics..

Author Message
TAGS:
Manager
Joined: 17 Dec 2008
Posts: 179
Followers: 1

Kudos [?]: 55 [0], given: 0

PS: Combinatorics.. [#permalink]  02 Mar 2009, 17:49
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 1 sessions
Tanya prepares 4 letters to be sent to 4 addresses. For each letter she prepared an envelope with correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only one letter will be put into the envelope with correct address?

A. 1/24
B. 1/8
C. 1/4
D. 1/3
E. 3/8
 Kaplan Promo Code Knewton GMAT Discount Codes Veritas Prep GMAT Discount Codes
SVP
Joined: 07 Nov 2007
Posts: 1828
Location: New York
Followers: 29

Kudos [?]: 541 [0], given: 5

Re: PS: Combinatorics.. [#permalink]  02 Mar 2009, 19:50
ConkergMat wrote:
Tanya prepares 4 letters to be sent to 4 addresses. For each letter she prepared an envelope with correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only one letter will be put into the envelope with correct address?

A. 1/24
B. 1/8
C. 1/4
D. 1/3
E. 3/8

You have 4 envelop and 4 letters--> Total no of ways = 4! =24

assume that 1234 -->only letter 1 will go to 1 other three will go into wrong enevelop

1-1 234 --> 432 234 -->342
only two possible solutions in this category
similarly when 2-2 other letters go to wrong address -->2 possible solutions.
similarly for 3-3 and 4-4
So No . of ways = 4C1 *2 = 8

p = 8/24 = 1/3
_________________

Smiling wins more friends than frowning

Manager
Joined: 01 Mar 2009
Posts: 52
Followers: 1

Kudos [?]: 1 [0], given: 2

Re: PS: Combinatorics.. [#permalink]  02 Mar 2009, 21:49
what is the C in 4C1*2=8?
Manager
Joined: 02 Mar 2009
Posts: 138
Followers: 1

Kudos [?]: 35 [0], given: 0

Re: PS: Combinatorics.. [#permalink]  16 Mar 2009, 00:16
It stands for combination.

Suresh, I think there is a minor error.

When you were explaining the 1-1 bit, the two possibilities of going wrong are:

234 --> 342 NOT 234 --> 432

Anyway, this was a minor error.

Thanks
Re: PS: Combinatorics..   [#permalink] 16 Mar 2009, 00:16
Similar topics Replies Last post
Similar
Topics:
1 PS Combinatorics 5 24 Apr 2013, 13:11
Combinatorics 4 04 Aug 2009, 12:38
PS - Combinatorics 11 18 Dec 2008, 10:17
25 PS - Combinatorics (m02q05) 39 12 Nov 2007, 17:36
Display posts from previous: Sort by