It is currently 20 Nov 2017, 12:26

### 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

# A bowl contains white and black balls. What is the

Author Message
TAGS:

### Hide Tags

CEO
Joined: 21 Jan 2007
Posts: 2734

Kudos [?]: 1076 [0], given: 4

Location: New York City
A bowl contains white and black balls. What is the [#permalink]

### Show Tags

06 Nov 2007, 09:33
5
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

66% (00:47) correct 34% (00:33) wrong based on 274 sessions

### HideShow timer Statistics

If a bowl contains only white and black balls, what is the probability of extracting a white ball from the bowl?

(1) There are twice as many white balls as black balls in the bowl

(2) If two balls are extracted from the bowl, the probability that both of them will be black is 0

M16-30
[Reveal] Spoiler: OA

Last edited by Bunuel on 26 Jul 2014, 09:21, edited 1 time in total.
Renamed the topic, edited the question and added the OA.

Kudos [?]: 1076 [0], given: 4

Manager
Joined: 01 Nov 2007
Posts: 68

Kudos [?]: 11 [0], given: 0

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

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 ?

Kudos [?]: 11 [0], given: 0

Senior Manager
Joined: 18 Jun 2007
Posts: 285

Kudos [?]: 63 [1], given: 0

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

06 Nov 2007, 10:09
1
KUDOS
1
This post was
BOOKMARKED
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.

Kudos [?]: 63 [1], given: 0

Manager
Joined: 04 Jan 2008
Posts: 83

Kudos [?]: 14 [1], given: 0

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

08 Jan 2008, 11:31
1
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

Kudos [?]: 14 [1], given: 0

SVP
Joined: 07 Nov 2007
Posts: 1790

Kudos [?]: 1088 [0], given: 5

Location: New York
Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

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
_________________

Smiling wins more friends than frowning

Kudos [?]: 1088 [0], given: 5

Manager
Joined: 27 Oct 2008
Posts: 185

Kudos [?]: 166 [0], given: 3

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

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.

Kudos [?]: 166 [0], given: 3

Manager
Status: Essaying
Joined: 27 May 2010
Posts: 144

Kudos [?]: 9 [0], given: 8

Location: Ghana
Concentration: Finance, Finance
Schools: Cambridge
GMAT 1: 690 Q47 V37
GPA: 3.9
WE: Accounting (Education)
Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

29 Nov 2011, 05:19
Going with A. Statement two says nothg about the number of white balls

Kudos [?]: 9 [0], given: 8

Senior Manager
Joined: 12 Oct 2011
Posts: 255

Kudos [?]: 63 [0], given: 110

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

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

Kudos [?]: 63 [0], given: 110

Manager
Joined: 29 Jul 2011
Posts: 104

Kudos [?]: 73 [0], given: 6

Location: United States
Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

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

Kudos [?]: 73 [0], given: 6

Non-Human User
Joined: 09 Sep 2013
Posts: 15621

Kudos [?]: 283 [0], given: 0

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

26 Jul 2014, 06:34
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 283 [0], given: 0

Non-Human User
Joined: 09 Sep 2013
Posts: 15621

Kudos [?]: 283 [0], given: 0

Re: A bowl contains white and black balls. What is the [#permalink]

### Show Tags

17 Aug 2015, 20:53
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 283 [0], given: 0

Re: A bowl contains white and black balls. What is the   [#permalink] 17 Aug 2015, 20:53
Display posts from previous: Sort by