Tough and tricky 6: Probability of drawing : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 23 Feb 2017, 11:07

### 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

# Tough and tricky 6: Probability of drawing

 post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 37100
Followers: 7250

Kudos [?]: 96422 [0], given: 10751

Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

11 Oct 2009, 17:17
Expert's post
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

78% (01:50) correct 22% (00:36) wrong based on 67 sessions

### HideShow timer Statistics

A bag contains 3 red, 4 black and 2 white balls. What is the probability of drawing a red and a white ball in two successive draws, each ball being put back after it is drawn?
(A) 2/27
(B) 1/9
(C) 1/3
(D) 4/27
(E) 2/9
_________________
Senior Manager
Joined: 18 Aug 2009
Posts: 328
Followers: 8

Kudos [?]: 304 [0], given: 13

Re: Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

11 Oct 2009, 17:45
Number of ways to choose Red ball = 3C1
Number of ways to choose White ball = 2C1
Total number of ways to choose 2 balls at random = 9C2

$$(3C1*2C1)*2C1/9C2 = 1/3$$
Manager
Joined: 06 Oct 2009
Posts: 69
Followers: 2

Kudos [?]: 34 [0], given: 5

Re: Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

11 Oct 2009, 22:57
I think its D i.e. 4/27

we can have either RW or WR combination in successive draws.

So the probability will be (3/9 x 2/9) + (2/9 x 3/9) = 4/27

OA pls???????
Intern
Joined: 07 Oct 2009
Posts: 19
Followers: 0

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

Re: Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

12 Oct 2009, 03:02
answer should be D

As we are replacing the balls so the probability of drawing two balls at random is 9*9

Ans = 3*2*2/(9*9)
Math Expert
Joined: 02 Sep 2009
Posts: 37100
Followers: 7250

Kudos [?]: 96422 [0], given: 10751

Re: Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

12 Oct 2009, 08:45
Set of Tough & tricky questions is now combined in one thread: tough-tricky-set-of-problms-85211.html

You can continue discussions and see the solutions there.
_________________
Senior Manager
Affiliations: SPG
Joined: 15 Nov 2006
Posts: 330
Followers: 14

Kudos [?]: 715 [0], given: 28

Re: Tough and tricky 6: Probability of drawing [#permalink]

### Show Tags

11 Feb 2011, 03:43

probability of getting RW = $$\frac{3}{9}*\frac{2}{9}$$
we could have RW or WR. in both cases, we'll have a red and a white ball.

total probability = $$\frac{3}{9}*\frac{2}{9}*2 = \frac{4}{27}$$

Ans: D

_________________

press kudos, if you like the explanation, appreciate the effort or encourage people to respond.

Re: Tough and tricky 6: Probability of drawing   [#permalink] 11 Feb 2011, 03:43
Similar topics Replies Last post
Similar
Topics:
4 Probability tough 4 28 Mar 2011, 08:39
Tricky Probability 4 27 Sep 2010, 14:25
6 Tough and tricky: Probability of integr being divisible by 8 9 11 Oct 2009, 17:33
1 Tough and tricky 2: 4 11 Oct 2009, 16:17
7 Tough and tricky: The sum of the even numbers. 7 11 Oct 2009, 16:11
Display posts from previous: Sort by

# Tough and tricky 6: Probability of drawing

 post reply Question banks Downloads My Bookmarks Reviews Important topics

 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®.