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

It is currently 21 Sep 2014, 06:11

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Sam and Angela decide to join a Dance club. The club

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
avatar
Joined: 15 Aug 2004
Posts: 329
Followers: 1

Kudos [?]: 4 [0], given: 0

GMAT Tests User
Sam and Angela decide to join a Dance club. The club [#permalink] New post 31 Jul 2006, 07:04
1. Sam and Angela decide to join a Dance club. The club includes 7 women and 7 men (including Sam and Angela). The club decides to select a woman and a man to lead the dance group. What is the probability that Sam and Angela will NOT be selected.

The Way to do this would be 1- 1/7* 1/7... But I wanted to ask that the ORDER is not important here and hence should the probab for them to be selected be 2/49 instead of 1/49.

2. What is the probab of selecting a woman and a man from a group of 7 women and 7 men.

Would this be 7C1 * 7C1/14C2 (As order does not matter here)

Basically what is the difference between the above two questions which makes the aproach different.
Manager
Manager
avatar
Joined: 26 Jun 2006
Posts: 154
Followers: 1

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

 [#permalink] New post 31 Jul 2006, 07:16
Here is my understanding of the problem and solution.

Let's first try to find probability of the opposite event: either Sam or Angela (or both) are selected to lead the dance.

There are 7 women (including Angela) to form a possible pair with Sam.
There are 6 men (excluding Sam, who was already counted above) to pair with Angela. So, we have 13 possible pairs including either Sam or Angela.

Total number of pairs is 7x7=49.

So, the probability is 1 - 13/49 = 36/49
Senior Manager
Senior Manager
avatar
Joined: 09 Aug 2005
Posts: 286
Followers: 1

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

GMAT Tests User
 [#permalink] New post 31 Jul 2006, 19:03
v1rok wrote:
Here is my understanding of the problem and solution.

Let's first try to find probability of the opposite event: either Sam or Angela (or both) are selected to lead the dance.

There are 7 women (including Angela) to form a possible pair with Sam.
There are 6 men (excluding Sam, who was already counted above) to pair with Angela. So, we have 13 possible pairs including either Sam or Angela.

Total number of pairs is 7x7=49.

So, the probability is 1 - 13/49 = 36/49



its sam and angela ---- not sam or angela - its basically the couple is not selected.

1- (1/7)(1/7) = = 48/49
Senior Manager
Senior Manager
avatar
Joined: 09 Aug 2005
Posts: 286
Followers: 1

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

GMAT Tests User
 [#permalink] New post 31 Jul 2006, 19:15
v1rok wrote:
Here is my understanding of the problem and solution.

Let's first try to find probability of the opposite event: either Sam or Angela (or both) are selected to lead the dance.

There are 7 women (including Angela) to form a possible pair with Sam.
There are 6 men (excluding Sam, who was already counted above) to pair with Angela. So, we have 13 possible pairs including either Sam or Angela.

Total number of pairs is 7x7=49.

So, the probability is 1 - 13/49 = 36/49



its sam and angela ---- not sam or angela - its basically the couple is not selected.

1- (1/7)(1/7) = = 48/49
Manager
Manager
avatar
Joined: 26 Jun 2006
Posts: 154
Followers: 1

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

 [#permalink] New post 31 Jul 2006, 19:46
Sorry, but I respectufully disagree

Let S be "Sam is selected",
A be "Angela is selected"

From set theory,

Event that "Sam and Angela not selected" can be written as

not(S and A) = not(S) or not(A),

and the latter translates into English as "neither Sam nor Angela selected."

I stand by my solution.

Is there OA?
Manager
Manager
avatar
Joined: 26 Jun 2006
Posts: 154
Followers: 1

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

 [#permalink] New post 31 Jul 2006, 19:52
Oops... Even though I provided correct justification in the post just above this one, I had solved for the wrong event in my original post at the top. Of course, the answer is 48/49. I just need to learn how to read properly...
SVP
SVP
avatar
Joined: 30 Mar 2006
Posts: 1741
Followers: 1

Kudos [?]: 27 [0], given: 0

GMAT Tests User
 [#permalink] New post 31 Jul 2006, 20:59
1)
Lets first find out the probability of selecting Sam and Angela
Probability of Selecting Sam = 1/7
Probability that angela is selected = 1
P1 = 1/7

Probability that angela is selected = 1/7
Probabilty the Sam is selected = 1

P2 = 1/7

P = P1*P2
P = 1/49
Probability that Sam and angela are not selected = 1 - 1/49 = 48/49

2) Probability of selecting a man = 1/7
Probabiltiy of selcting a woman = 1/7

Probability of selecting a man and a woman = 1/7 * 1/7 = 1/49
Senior Manager
Senior Manager
avatar
Joined: 15 Aug 2004
Posts: 329
Followers: 1

Kudos [?]: 4 [0], given: 0

GMAT Tests User
 [#permalink] New post 01 Aug 2006, 03:17
jaynayak wrote:
1)
Lets first find out the probability of selecting Sam and Angela
Probability of Selecting Sam = 1/7
Probability that angela is selected = 1
P1 = 1/7

Probability that angela is selected = 1/7
Probabilty the Sam is selected = 1

P2 = 1/7

P = P1*P2
P = 1/49
Probability that Sam and angela are not selected = 1 - 1/49 = 48/49

2) Probability of selecting a man = 1/7
Probabiltiy of selcting a woman = 1/7

Probability of selecting a man and a woman = 1/7 * 1/7 = 1/49


Jaynayak...

Why is this method wrong here .... 7C1 * 7C1/14C2

The order does not matter, so can't we use the above method as we did in earlier questions...
Senior Manager
Senior Manager
avatar
Joined: 09 Aug 2005
Posts: 286
Followers: 1

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

GMAT Tests User
 [#permalink] New post 01 Aug 2006, 18:43
sumitsarkar82 wrote:
jaynayak wrote:
1)
Lets first find out the probability of selecting Sam and Angela
Probability of Selecting Sam = 1/7
Probability that angela is selected = 1
P1 = 1/7

Probability that angela is selected = 1/7
Probabilty the Sam is selected = 1

P2 = 1/7

P = P1*P2
P = 1/49
Probability that Sam and angela are not selected = 1 - 1/49 = 48/49

2) Probability of selecting a man = 1/7
Probabiltiy of selcting a woman = 1/7

Probability of selecting a man and a woman = 1/7 * 1/7 = 1/49


Jaynayak...

Why is this method wrong here .... 7C1 * 7C1/14C2

The order does not matter, so can't we use the above method as we did in earlier questions...


jaynayak is correct if we are talking about probability that the reqd couple is selected when male-female couples are selected.


7C1 * 7C1/14C2 assumes - two men or two women can be be selected as well -
SVP
SVP
avatar
Joined: 30 Mar 2006
Posts: 1741
Followers: 1

Kudos [?]: 27 [0], given: 0

GMAT Tests User
 [#permalink] New post 01 Aug 2006, 20:02
old_dream_1976 wrote:
sumitsarkar82 wrote:
jaynayak wrote:
1)
Lets first find out the probability of selecting Sam and Angela
Probability of Selecting Sam = 1/7
Probability that angela is selected = 1
P1 = 1/7

Probability that angela is selected = 1/7
Probabilty the Sam is selected = 1

P2 = 1/7

P = P1*P2
P = 1/49
Probability that Sam and angela are not selected = 1 - 1/49 = 48/49

2) Probability of selecting a man = 1/7
Probabiltiy of selcting a woman = 1/7

Probability of selecting a man and a woman = 1/7 * 1/7 = 1/49


Jaynayak...

Why is this method wrong here .... 7C1 * 7C1/14C2

The order does not matter, so can't we use the above method as we did in earlier questions...


jaynayak is correct if we are talking about probability that the reqd couple is selected when male-female couples are selected.


7C1 * 7C1/14C2 assumes - two men or two women can be be selected as well -


Thats your answer. 7C! can represent men or women. Hence not conclusive.
Senior Manager
Senior Manager
avatar
Joined: 15 Aug 2004
Posts: 329
Followers: 1

Kudos [?]: 4 [0], given: 0

GMAT Tests User
 [#permalink] New post 03 Aug 2006, 03:47
jaynayak wrote:
old_dream_1976 wrote:
sumitsarkar82 wrote:
jaynayak wrote:
2) Probability of selecting a man = 1/7
Probabiltiy of selcting a woman = 1/7

Probability of selecting a man and a woman = 1/7 * 1/7 = 1/49


Jaynayak...

Why is this method wrong here .... 7C1 * 7C1/14C2

The order does not matter, so can't we use the above method as we did in earlier questions...


jaynayak is correct if we are talking about probability that the reqd couple is selected when male-female couples are selected.


7C1 * 7C1/14C2 assumes - two men or two women can be be selected as well -


Thats your answer. 7C! can represent men or women. Hence not conclusive.


For two men or two women shouldn't it be 7C2/14C2

Once a Man has been selected we will not have 7 options to choose from...

I am a bit confused here... Plz help

Also, what if the question said - Prob for Selecting 2 men and a woman... how would we approach it then...
CEO
CEO
User avatar
Joined: 20 Nov 2005
Posts: 2922
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Followers: 15

Kudos [?]: 81 [0], given: 0

GMAT Tests User
Re: Probability Questions [#permalink] New post 03 Aug 2006, 08:21
sumitsarkar82 wrote:
1. Sam and Angela decide to join a Dance club. The club includes 7 women and 7 men (including Sam and Angela). The club decides to select a woman and a man to lead the dance group. What is the probability that Sam and Angela will NOT be selected.

The Way to do this would be 1- 1/7* 1/7... But I wanted to ask that the ORDER is not important here and hence should the probab for them to be selected be 2/49 instead of 1/49.

2. What is the probab of selecting a woman and a man from a group of 7 women and 7 men.

Would this be 7C1 * 7C1/14C2 (As order does not matter here)

Basically what is the difference between the above two questions which makes the aproach different.


Two questions are altogether different.
In the first question you can select any male except Sam AND can select any female except Angela. Th egroup of two must have one male and one female.
Total cases = 7C1 * 7C1 = 49
How many cases when Sam and Angela are selected = 1
Prob of NOT selecting these two = 1-1/49 = 48/49

Second question is asking the probability of selecting a particular man and a particular woman out of 7 men and 7 women.
In how many ways you can select any man and any women = 7C1 * 7C1 = 49
Ways when a particular man and a particular woman are selected = 1
Prob = 1/49

If second question asks: What is the probabilty of selecting 2 people from 7 men and 7 women so that the group of 2 have 1 man and 1 woman then the answer is
Total cases = 14C2 = 91
Cases when both are men = 7C2 = 21
Cases when both are women = 7C2 = 21
Cases when one is man and one is woman = 91 -42 = 49
Prob = 49/91 or 7C1 * 7C1/14C2

Hope this helps.
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

Re: Probability Questions   [#permalink] 03 Aug 2006, 08:21
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic Joining the GMAT club anirudhvyas 2 18 May 2010, 07:54
1 Experts publish their posts in the topic Clubs to join for "leadership experience" GmatNY86 12 27 Oct 2009, 10:35
The students in a certain class each joined a club, arjtryarjtry 1 30 Jul 2008, 17:46
How many Clubs to join IHATEMELGIBSON1 4 05 Jul 2007, 08:08
Yippee........I joined d 700 CLUB nna bros 3 04 May 2007, 11:51
Display posts from previous: Sort by

Sam and Angela decide to join a Dance club. The club

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.