Find all School-related info fast with the new School-Specific MBA Forum
Learn more about the recent changes... close

It is currently 24 May 2013, 21:35
Customize  |  Hide

Search
Register
New posts
Unanswered

A bowl contains white and black balls. What is the

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
TAGS:
CEO
CEO
User avatar
Joined: 21 Jan 2007
Posts: 2797
Location: New York City
Followers: 5

Kudos [?]: 132 [0], given: 4

GMAT Tests User
A bowl contains white and black balls. What is the [#permalink] New post 06 Nov 2007, 09:33
00:00

Question Stats:

75% (01:59) correct 25% (01:11) wrong based on 0 sessions
A bowl contains white and black balls.
What is the probability to extract a white ball from the bowl?

1. There are twice as many white balls as black balls
2. If two balls are extracted from the bowl, the probability that both of them are black is 0
Manager
Manager
Joined: 01 Nov 2007
Posts: 69
Followers: 1

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

 [#permalink] New post 06 Nov 2007, 09:59
I will go with A

1. Since there are twice as many white balls as black balls.
Probability to extract a white ball will be 2/3

2. "If two balls are extracted from the bowl, the probability that both of them are black is 0"
This is only possible when either there is no black ball or either 1 black ball. So we cannot determine the probability of extracting a white ball...


Am I correct ?
Senior Manager
Senior Manager
Joined: 18 Jun 2007
Posts: 300
Followers: 2

Kudos [?]: 12 [0], given: 0

GMAT Tests User
 [#permalink] New post 06 Nov 2007, 10:09
sportyrizwan wrote:
I will go with A

1. Since there are twice as many white balls as black balls.
Probability to extract a white ball will be 2/3

2. "If two balls are extracted from the bowl, the probability that both of them are black is 0"
This is only possible when either there is no black ball or either 1 black ball. So we cannot determine the probability of extracting a white ball...


Am I correct ?


Yup sporty. Just one clearification.

I assume that sufficiency of A is pretty clear.

As far as B is concern, black ball cant not be 0 since question states that
A bowl contains white and black balls

So it is clear that there is 1 black ball.
Why B is insufficient?

assume there are only 1 black and 1 white ball- probability to extract a white ball from the bowl= 1/2

Now assume there are 3 white balls and 1 black ball - probability to extract a white ball from the bowl is 3/4

B is insufficient. Answer is A.
1 KUDOS received
Manager
Manager
User avatar
Joined: 04 Jan 2008
Posts: 86
Followers: 1

Kudos [?]: 10 [1] , given: 0

Re: zero probability [#permalink] New post 08 Jan 2008, 11:31
1
This post received
KUDOS
A
S1 gives 2/3- suffi
S2 gives, prob both black=0, which says that there is only one black ball in there. So, the no of white balls can be anything, so we cant find prob of white= s2 not suffi
SVP
SVP
User avatar
Joined: 07 Nov 2007
Posts: 1842
Location: New York
Followers: 20

Kudos [?]: 291 [0], given: 5

GMAT Tests User
Re: zero probability [#permalink] New post 26 Aug 2008, 13:00
bmwhype2 wrote:
A bowl contains white and black balls.
What is the probability to extract a white ball from the bowl?

1. There are twice as many white balls as black balls
2. If two balls are extracted from the bowl, the probability that both of them are black is 0


A

State 1 :
W:B= 2n:n

p= 2nC1/3nC1 = 2/3

state 2:
two possibilities that all are WHITE balls OR one Black ball and others are White.
insuffcieint
_________________

Your attitude determines your altitude
Smiling wins more friends than frowning

Manager
Manager
Joined: 27 Oct 2008
Posts: 188
Followers: 1

Kudos [?]: 42 [0], given: 3

GMAT Tests User
Re: zero probability [#permalink] New post 28 Sep 2009, 11:07
A bowl contains white and black balls.
What is the probability to extract a white ball from the bowl?

1. There are twice as many white balls as black balls
2. If two balls are extracted from the bowl, the probability that both of them are black is 0

Soln.

Statement 1 alone is sufficient.
Assuming that there are x black balls. Hence 2x white balls.
Thus probability of drawing a white ball is = 2x/3x = 2/3

Statement 2 alone is not sufficient.
From this statement we cannot guess the number of white and black balls present.
Manager
Manager
Status: Essaying
Joined: 27 May 2010
Posts: 158
Location: Ghana
Concentration: Finance, Finance
Schools: Cambridge
GMAT 1: 690 Q47 V37
GPA: 3.9
WE: Accounting (Education)
Followers: 1

Kudos [?]: 7 [0], given: 8

GMAT ToolKit User GMAT Tests User
Re: A bowl contains white and black balls. What is the [#permalink] New post 29 Nov 2011, 05:19
Going with A. Statement two says nothg about the number of white balls
Senior Manager
Senior Manager
Joined: 12 Oct 2011
Posts: 283
Followers: 0

Kudos [?]: 13 [0], given: 110

Re: A bowl contains white and black balls. What is the [#permalink] New post 04 Jan 2012, 12:54
Clearly A. Statement 1 gives us the probability as 2/3 and statement 2 does not gives us any information regarding the number of white balls or the total number of balls.
_________________

Consider KUDOS if you feel the effort's worth it

Manager
Manager
User avatar
Joined: 29 Jul 2011
Posts: 113
Location: United States
Followers: 1

Kudos [?]: 21 [0], given: 6

GMAT Tests User
Re: A bowl contains white and black balls. What is the [#permalink] New post 04 Jan 2012, 13:25
The stem can be rephrased as w/(w+b)?

1. w = 2b. Sufficient by substitution
2. This means that there is only one black ball. Let t = total, so black = 1 and white = t - 1. This implies (t-1)/[(t-1)+1] = (t-1)/t. We don't know the total, so insufficient

A.
_________________

I am the master of my fate. I am the captain of my soul.
Please consider giving +1 Kudos if deserved!

DS - If negative answer only, still sufficient. No need to find exact solution.
PS - Always look at the answers first
CR - Read the question stem first, hunt for conclusion
SC - Meaning first, Grammar second
RC - Mentally connect paragraphs as you proceed. Short = 2min, Long = 3-4 min

Re: A bowl contains white and black balls. What is the   [#permalink] 04 Jan 2012, 13:25
    Similar topics Author Replies Last post
Similar
Topics:
 New posts A bag contains 3 red, 4 black and 2 white balls. What is the shubhangi 2 24 Dec 2003, 21:26
New posts A bag contains 3 red, 4 black and 2 white balls. What is the Keen 8 26 Jul 2004, 10:33
New posts The bowl contains only white and black balls. What is the arjtryarjtry 3 02 Sep 2008, 05:30
New posts If a bowl contains only white and black balls, what is the Economist 2 21 Sep 2009, 04:50
New posts If a bowl contains only white and black balls, what is the gmat1220 2 16 Mar 2011, 17:45
Display posts from previous: Sort by

A bowl contains white and black balls. What is the

  Question banks Downloads My Bookmarks Reviews  
Print view
First unread post

Moderators: Bunuel, VeritasPrepKarishma, IanStewart

Search for:


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®.

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com