It is currently 22 Feb 2018, 12:51

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

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

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43867
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 29 Jan 2018, 05:28
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

74% (00:49) correct 26% (00:41) wrong based on 23 sessions

HideShow 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.
[Reveal] Spoiler: OA

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

BSchool Forum Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 2068
Location: India
GPA: 3.12
Premium Member CAT Tests
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 29 Jan 2018, 05:34
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)
_________________

Stay hungry, Stay foolish

2017-2018 MBA Deadlines

Class of 2020: Rotman Thread | Schulich Thread
Class of 2019: Sauder Thread

1 KUDOS received
Senior Manager
Senior Manager
User avatar
G
Joined: 17 Oct 2016
Posts: 327
Location: India
Concentration: Operations, Strategy
GPA: 3.73
WE: Design (Real Estate)
GMAT ToolKit User Premium Member CAT Tests
A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 29 Jan 2018, 05:47
1
This post received
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
_________________

Help with kudos if u found the post useful. Thanks


Last edited by Sasindran on 29 Jan 2018, 06:22, edited 1 time in total.
Intern
Intern
avatar
B
Joined: 24 Jun 2013
Posts: 29
GMAT ToolKit User CAT Tests
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 29 Jan 2018, 06:16
P(RorW)= r/(9r+6) + (3r+2)/(9r+6) = 2/3
Intern
Intern
avatar
B
Joined: 28 Jul 2016
Posts: 14
Location: India
GMAT 1: 680 Q50 V32
GPA: 3.97
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 29 Jan 2018, 09:28
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
Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2001
Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar [#permalink]

Show Tags

New post 30 Jan 2018, 10:14
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
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: A bag contains r red marbles, 5r + 4 white marbles and 3r + 2 blue mar   [#permalink] 30 Jan 2018, 10:14
Display posts from previous: Sort by

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

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.