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

It is currently 28 Aug 2016, 02:33
GMAT Club Tests

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

Probabilities Question

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 15 Sep 2005
Posts: 13
Location: London
Followers: 0

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

Probabilities Question [#permalink]

Show Tags

New post 15 Sep 2005, 13:15
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Hi again, I got another question, this time about probabilities:

There are 10 different stamps. Peter's collection includes 3 stamps of the 10. If 2 stamps are drawn from the 10, what is the probability that neither of the 2 stamps are among the 3 held by Peter?

Thanks!

M
VP
VP
avatar
Joined: 22 Aug 2005
Posts: 1120
Location: CA
Followers: 1

Kudos [?]: 85 [0], given: 0

 [#permalink]

Show Tags

New post 15 Sep 2005, 13:29
Lets first find probability when BOTH two stamps drawn are from the Peter's collection of 3 stamps. The probability for this would be:

3C2 / 10C2 = 3/45 = 1/15

Probability that ONE of the stamp picked matched that of Peter's collection =

3C1 / 10C2 = 3/45 = 1/15

the probability that NIETHER was from Peter's collection = 1 - 1/15 - 1/15 or
p = 13/15

Last edited by duttsit on 15 Sep 2005, 14:51, edited 1 time in total.
Senior Manager
Senior Manager
avatar
Joined: 29 Nov 2004
Posts: 484
Location: Chicago
Followers: 1

Kudos [?]: 21 [0], given: 0

 [#permalink]

Show Tags

New post 15 Sep 2005, 14:00
7/10*6/9 = 7/15
_________________

Fear Mediocrity, Respect Ignorance

VP
VP
avatar
Joined: 22 Aug 2005
Posts: 1120
Location: CA
Followers: 1

Kudos [?]: 85 [0], given: 0

 [#permalink]

Show Tags

New post 15 Sep 2005, 14:33
ranga41 wrote:
7/10*6/9 = 7/15


hows the second draw probability 6/9 here? wont it depend on first draw. I mean if:
A) first draw resulted into one of the stamp in peter's collection, this probability would be : 7/9

B) first draw did not result into perter's collection stamps, second draw probability would be:
6/9

As first draw probability remains same, the total probability would be:

7/10 * 7/9 + 7/10 * 6/9 or 91/90

Guess ans to this question depends/changes on if:
- both stamps are drawn "together"
- stamps are drawn one after another.

The ans will vary based on the two.

Last edited by duttsit on 15 Sep 2005, 15:00, edited 2 times in total.
Intern
Intern
avatar
Joined: 05 May 2005
Posts: 44
Followers: 1

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

 [#permalink]

Show Tags

New post 15 Sep 2005, 14:35
First pick: 7/10 stamps are NOT included in Peter's collection
Second pick: 6/9 stamps are NOT included in Peter's collection, since there are 9 stamps left and 3 of those 9 are within his collection

7/10 * 6/9 = 7/15
Intern
Intern
avatar
Joined: 14 Jun 2005
Posts: 37
Followers: 1

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

 [#permalink]

Show Tags

New post 15 Sep 2005, 22:21
Can we use binomial distribution here ?????

10C2*(7/10)^2*(3/10)^8
Intern
Intern
avatar
Joined: 09 Sep 2005
Posts: 18
Followers: 0

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

 [#permalink]

Show Tags

New post 16 Sep 2005, 06:50
You draw first time and it is 7/10 to miss
Then you draw second time and it 6/9 to miss
So - 6*7/90
Manager
Manager
avatar
Joined: 06 Aug 2005
Posts: 197
Followers: 3

Kudos [?]: 8 [0], given: 0

 [#permalink]

Show Tags

New post 20 Sep 2005, 05:41
silentell wrote:
First pick: 7/10 stamps are NOT included in Peter's collection
Second pick: 6/9 stamps are NOT included in Peter's collection, since there are 9 stamps left and 3 of those 9 are within his collection

7/10 * 6/9 = 7/15


7/15 looks good to me.

I think that the suggestion of 91/90 is improbable, indeed impossible !

0<= P <= 1 for all probabilities.
Intern
Intern
avatar
Joined: 16 Aug 2005
Posts: 25
Location: India
Followers: 0

Kudos [?]: 3 [0], given: 0

 [#permalink]

Show Tags

New post 20 Sep 2005, 06:47
don't overthink it. It is as simple as 7c2/10c2= 7/15
  [#permalink] 20 Sep 2005, 06:47
Display posts from previous: Sort by

Probabilities Question

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| 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®.