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

It is currently 23 Jul 2014, 08:14

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

a certain jar contains only b black marbles, w white

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
User avatar
Joined: 17 Jan 2006
Posts: 92
Followers: 1

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

a certain jar contains only b black marbles, w white [#permalink] New post 03 Jun 2006, 22:21
a certain jar contains only b black marbles, w white marbles, and r red marbles. If one marble is to be chosen at random from the jar, is the probability that the marble chosen will be red greater than the probability that the marble chosen will be white?
(1)r/(b+w) > w/(b+r)
(2) b-w>r
Manager
Manager
avatar
Joined: 29 Apr 2006
Posts: 86
Followers: 1

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

Re: GMATPREP : marble probability [#permalink] New post 04 Jun 2006, 11:12
shobhitb wrote:
dinesh8 wrote:
a certain jar contains only b black marbles, w white marbles, and r red marbles. If one marble is to be chosen at random from the jar, is the probability that the marble chosen will be red greater than the probability that the marble chosen will be white?
(1)r/(b+w) > w/(b+r)
(2) b-w>r


A


Can you explain how you got A?
Senior Manager
Senior Manager
avatar
Joined: 12 Mar 2006
Posts: 372
Schools: Kellogg School of Management
Followers: 2

Kudos [?]: 27 [0], given: 3

GMAT Tests User
 [#permalink] New post 04 Jun 2006, 12:29
my guess A

2...does not help since it implies b > r+w

to say that the probability of choosing a red marble is higher than that of choosing a white marble we need to prove rC1/(r+w+b)C1 > wC1/(r+w+b)C1...i.e r>w

1 is r/(b+w) > w/(b+r)

i.e r(b+r) > w(b+w)

i.e br + r^2 > bw + w^2

i.e (r-w)(r+w) + b(r-w) > 0

since r,b,w are positive #'s this is possible only when r > w

so A
Intern
Intern
User avatar
Joined: 04 May 2006
Posts: 49
Followers: 0

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

 [#permalink] New post 05 Jun 2006, 00:41
I think its A.
Option 1) - It doesn't give complete info.
Option 2) -
Required probability for red is r/(r+w+b)
Required probability for white is w/(r+w+b)

From Eqn 1) we know that r/(b+w) > w/(b+r)
So by componendo & dividendo (C & D)
r/(b+w+r) > w/(b+r+w)
which is sufficient to answer this.

Please update if my approach is not correct.

_________________

If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut.
Albert Einstein

  [#permalink] 05 Jun 2006, 00:41
    Similar topics Author Replies Last post
Similar
Topics:
14 Experts publish their posts in the topic A certain jar contains only b black marbles, w white marbles anilnandyala 9 16 Nov 2010, 05:43
A certain jar contains only b black marbles, w white uzonwagba 3 24 Jul 2009, 12:23
3 Experts publish their posts in the topic A certain jar contains only b black marbles, w white marbles jimjohn 12 26 Dec 2007, 19:07
A certain jar contains only w white marbles b black marbles tlntd42 4 29 Jul 2007, 23:21
A certain jar contains only b black marbles, w white marbles nitinneha 6 04 Apr 2007, 15:47
Display posts from previous: Sort by

a certain jar contains only b black marbles, w white

  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®.