NEW HERE? LEARN MORE
closeclose
Last visit was: 13 May 2024, 09:11 It is currently 13 May 2024, 09:11
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 93242
Own Kudos [?]: 623435 [1]
Given Kudos: 81851
Send PM
CAT Tests Forum Quiz Mode
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   29 Jan 2018, 06:28
1
Kudos
Expert Reply
00:00
A
B
C
D
E

Difficulty:

25% (medium)

Question Stats:

75% (01:25) correct 25% (01:41) wrong based on 101 sessions
Hide Show timer Statistics
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue marbles. If there are only red, white and blue marbles in the bag, what is the probability of pulling a red or white marble?

A. 1/9
B. 1/3
C. 2/3
D. 8/9
E. Cannot be determined.
ShowHide Answer
Official Answer
C
User avatar
G
Sasindran
Senior Manager
Senior Manager
Joined: 17 Oct 2016
Posts: 258
Own Kudos [?]: 307 [1]
Given Kudos: 127
Location: India
Concentration: Operations, Strategy
GPA: 3.73
WE:Design (Real Estate)
Send PM
GMAT ToolKit User
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   Updated on: 29 Jan 2018, 07:22
1
Kudos
C

Total marbles = r + 5r + 4 + 3r + 2 = 9r+6.

Probability of getting red marbles = r/(9r+6)
Probability of getting white marbles = (5r+4)/(9r+6)

Hence, Probability of getting red or white marbles = r/(9r+6) + (5r+4)/(9r+6)
= (6r+4)/(9r+6)
= 2(3r+2)/(3(3r+2)
= 2/3

Originally posted by Sasindran on 29 Jan 2018, 06:47.
Last edited by Sasindran on 29 Jan 2018, 07:22, edited 1 time in total.
User avatar
L
pushpitkc
CEO
CEO
Joined: 26 Feb 2016
Posts: 2873
Own Kudos [?]: 5221 [0]
Given Kudos: 47
Location: India
GPA: 3.12
Send PM
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   29 Jan 2018, 06:34
Bunuel wrote:
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue marbles. If there are only red, white and blue marbles in the bag, what is the probability of pulling a red or white marble?

A. 1/9
B. 1/3
C. 2/3
D. 8/9
E. Cannot be determined.



Since there are r red marbles, 5r+4 white marbles, and 3r+2 blue marbles,
there will be a total of 9r+6

Lets assume an arbitrary value for r=1. Now, there is 1 red marble, 9 white marbles, and 5 blue marbles.

Therefore, the probability of pulling a red or white marble in this case will be \(\frac{1+9}{1+9+5} = \frac{10}{15} = \frac{2}{3}\)(Option C)

Traditional Approach

Probability = \(\frac{P(Red,White)}{P(Total)} = \frac{r+5r+4}{9r+6} = \frac{6r+4}{9r+6} = \frac{2}{3}\)(Option C)
avatar
P
doomedcat
Manager
Manager
Joined: 24 Jun 2013
Posts: 120
Own Kudos [?]: 319 [0]
Given Kudos: 124
Location: India
Schools: ISB '20 GMBA '20
GMAT 1: 680 Q47 V36
Send PM
GMAT ToolKit User
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   29 Jan 2018, 07:16
P(RorW)= r/(9r+6) + (3r+2)/(9r+6) = 2/3
User avatar
L
globaldesi
VP
VP
Joined: 28 Jul 2016
Posts: 1210
Own Kudos [?]: 1732 [0]
Given Kudos: 67
Location: India
Concentration: Finance, Human Resources
Schools: ISB '18 (D)
GPA: 3.97
WE:Project Management (Investment Banking)
Send PM
Reviews Badge
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   29 Jan 2018, 10:28
Agree with solutions. Since its or hence net probability should be the sum of finding either red marbles or white marbles.
Hence total probability is
Prob of finding red marbles = r/(9r+6)

Prob of finding white marbles= (5r+4)/(9r+6)

sum = r/(9r+6)+ (5r+6)/(9r+6) =6r+4/9r+6 = 2/3
hence C
User avatar
P
JeffTargetTestPrep
Target Test Prep Representative
Joined: 04 Mar 2011
Status:Head GMAT Instructor
Affiliations: Target Test Prep
Posts: 3042
Own Kudos [?]: 6341 [0]
Given Kudos: 1646
Send PM
Forum Quiz Mode
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   30 Jan 2018, 11:14
Expert Reply
Bunuel wrote:
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue marbles. If there are only red, white and blue marbles in the bag, what is the probability of pulling a red or white marble?

A. 1/9
B. 1/3
C. 2/3
D. 8/9
E. Cannot be determined.


The total number of marbles is r + (5r + 4) + (3r + 2) = 9r + 6. The total number of marbles that are either red or white is r + 5r + 4 = 6r + 4. Thus, the probability of pulling a red or a white marble is:

(6r + 4)/(9r + 6)

2(3r + 2)/[3(3r + 2)]

2/3

Answer: C
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32974
Own Kudos [?]: 828 [0]
Given Kudos: 0
Send PM
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink] New post   04 Mar 2021, 02:43
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.
GMAT Club Bot
gmatclubot
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]
04 Mar 2021, 02:43
Moderators:
Bunuel
Math Expert
93242 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3136 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions