Last visit was: 05 Nov 2024, 14:35 It is currently 05 Nov 2024, 14:35
Decision Tracker
My Rewards
New comers' posts
New posts
Unanswered

Close

GRE Prep 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 GRE 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
PREVIOUS TOPIC
NEXT TOPIC

A jar contains 4 marbles: 2 red and 2 white. 2 marbles are

Tags :
Find Similar Topics  About  Add a Tag

Show Tags
Hide Tags

avatar
SJ
Intern
Intern
Joined: 06 Nov 2016
Posts: 2
Own Kudos [?]: 16 [9]
Given Kudos: 0
Send PM
A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   Updated on: 07 Nov 2016, 01:29
2
7
Bookmarks
00:00

Question Stats:

53% (01:06) correct 46% (00:54) wrong based on 122 sessions

Hide Show timer Statistics

A jar contains 4 marbles: 2 red and 2 white. 2 marbles are chosen at random.

Quantity A
Quantity B
The probability that the marbles chosen are the same colour
The probability that the marbles chosen are different colours.



A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.
ShowHide Answer
Official Answer
B

Originally posted by SJ on 06 Nov 2016, 13:06.
Last edited by Carcass on 07 Nov 2016, 01:29, edited 1 time in total.
Edited by Carcass
Most Helpful Expert Reply
User avatar
sandy
Retired Moderator
Joined: 07 Jun 2014
Posts: 4813
Own Kudos [?]: 11137 [6]
Given Kudos: 0
GRE 1: Q167 V156
WE:Business Development (Energy and Utilities)
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   06 Nov 2016, 13:36
6
Expert Reply
Here,

Quantity A:

P(The probability that the marbles chosen are the same color)= P(RED)*P(RED)+P(BLUE)*P(BLUE) = \(\frac{2}{4}*\frac{1}{3} + \frac{2}{4}*\frac{1}{3}\)

= \(\frac{1}{3}\)

Quantity B:

P(The probability that the marbles chosen are different colours) = P(RED)*P(BLUE)+P(BLUE)*P(RED)
=\(\frac{2}{4}*\frac{2}{3}+\frac{2}{4}*\frac{2}{3}\)
=\(\frac{2}{3}\)

Hence Quantity B is greater.
General Discussion
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 29894
Own Kudos [?]: 36129 [0]
Given Kudos: 25919
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   07 Nov 2016, 01:30
Expert Reply
Please follow the rules how to post a question

qq-how-to-post-a-gre-question-the-easy-way-2357.html

Thank you
User avatar
P
GreenlightTestPrep
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12176 [0]
Given Kudos: 136
Send PM

Top Member of the Month
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   13 Nov 2016, 07:30
1
SJ wrote:
A jar contains 4 marbles: 2 red and 2 white. 2 marbles are chosen at random.

Quantity A
Quantity B
The probability that the marbles chosen are the same colour
The probability that the marbles chosen are different colours.




Here's a quick approach.

First pick 1 marble, ANY marble. For this first step, picking either color is equally likely.
At this point, there are 3 marbles remaining in the jar. 1 marble is the SAME color as the first marble you selected, and 2 marbles are a DIFFERENT color from the first marble you selected.
So, it's more likely that the two marbles will be DIFFERENT colors
Answer:
Show: ::
B


Mathematically, P(matching colors) = 1/3 and P(different colors) = 2/3
avatar
kairapotato
Intern
Intern
Joined: 20 Jul 2021
Posts: 3
Own Kudos [?]: 2 [0]
Given Kudos: 7
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   12 Oct 2021, 06:43
sandy wrote:
Here,

Quantity A:

P(The probability that the marbles chosen are the same color)= P(RED)*P(RED)+P(BLUE)*P(BLUE) = \(\frac{2}{4}*\frac{1}{3} + \frac{2}{4}*\frac{1}{3}\)

= \(\frac{1}{3}\)

Quantity B:

P(The probability that the marbles chosen are different colours) = P(RED)*P(BLUE)+P(BLUE)*P(RED)
=\(\frac{2}{4}*\frac{2}{3}+\frac{2}{4}*\frac{2}{3}\)
=\(\frac{2}{3}\)

Hence Quantity B is greater.


Why is 1W,1R not the same as 1R,1W?

If its random, why is it a permutation and not combination?
User avatar
P
GreenlightTestPrep
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12176 [0]
Given Kudos: 136
Send PM

Top Member of the Month
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   12 Oct 2021, 10:31
kairapotato wrote:
Why is 1W,1R not the same as 1R,1W?

If its random, why is it a permutation and not combination?


Here's a question that may help answer your question.

A bag contains 1 red marble and 1 white marble.
If you randomly select two marbles without replacement, what is the probability that the two marbles will be different colors?
Well, we know for certain that the probability is 1, since we can be guaranteed the two marbles will be different colors.

So when calculating the probability, we must treat WR and RW has different outcomes, otherwise are probability calculations
avatar
S
void
Senior Manager
Senior Manager
Joined: 03 Dec 2020
Posts: 440
Own Kudos [?]: 60 [0]
Given Kudos: 68
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   13 Oct 2021, 12:09
value of quant B = 4/4 * 3/4=3/4, right ?
because any marble is ok with us and next marble with same colour or not it doesn't matter, right ?
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 29894
Own Kudos [?]: 36129 [0]
Given Kudos: 25919
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   13 Oct 2021, 12:50
Expert Reply
void wrote:
value of quant B = 4/4 * 3/4=3/4, right ?
because any marble is ok with us and next marble with same colour or not it doesn't matter, right ?


See the explanation above by Brent. A bit of common sense will give you a fastest solution
avatar
B
Kimberly99
Manager
Manager
Joined: 10 Feb 2023
Posts: 76
Own Kudos [?]: 13 [0]
Given Kudos: 172
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   24 Feb 2023, 02:01
Hi Bernt GreenlightTestPrep

2 marbles are a DIFFERENT color from the first marble you selected.
So, it's more likely that the two marbles will be DIFFERENT colors : 2/3

To clarify here have the question been 2R and 3W then the calculation will be as usual Probability calculation right?
Probability of different colour( 2/5 * 1/4)
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 29894
Own Kudos [?]: 36129 [0]
Given Kudos: 25919
Send PM
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink] New post   24 Feb 2023, 04:39
Expert Reply
I think Brent explained how to handle the question in the following way very smart

Quote:
First pick 1 marble, ANY marble. For this first step, picking either color is equally likely.
At this point, there are 3 marbles remaining in the jar. 1 marble is the SAME color as the first marble you selected, and 2 marbles are a DIFFERENT color from the first marble you selected.
So, it's more likely that the two marbles will be DIFFERENT colors
Answer:
Prep Club for GRE Bot
gmatclubot
Re: A jar contains 4 marbles: 2 red and 2 white. 2 marbles are [#permalink]
24 Feb 2023, 04:39
Moderators:
adewale223
GRE Instructor
77 posts
bronaugust
GRE Forum Moderator
37 posts
BrushMyQuant
Moderator
1111 posts
VibhuAnurag
GRE Instructor
228 posts

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

Main navigation

Partners

GRE Resources

www.ets.org/gre | About | Terms and Conditions and Privacy Policy | Prep Club for GRE Rules | Contact