GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video
close
It is currently 27 May 2022, 04:34
Register
GMAT Club Tests
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 3 white balls, 3 black balls & 2 red balls
24 posts Go to First Unread Post
Print view
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
SORT BY:
Date
Kudos
   1   2 
Tags:
Find Similar Topics 

Show Tags
Hide Tags

User avatar
G
Temurkhon
Senior Manager
Senior Manager
Joined: 23 Jan 2013
Posts: 451
Schools: Cambridge'16
Re: A bag contains 3 white balls, 3 black balls & 2 red balls [#permalink] New post  02 Aug 2015, 04:22
First option (first two balls are not red and the last is red): 6/8*5/7*2/6=5/28

Second option (first or second ball is red and the last is red): (6/8*2/7*1/6)*2=2/28

So, 5/28+2/28=7/28=1/4

A
avatar
oanhnguyen1116
Intern
Intern
Joined: 07 Jan 2016
Posts: 19
Schools: AGSM '18
Re: A bag contains 3 white balls, 3 black balls & 2 red balls [#permalink] New post  13 Mar 2016, 06:02
Could you tell me more about your way to give that formula? Thank you.

zisis wrote:
Bunuel wrote:
krishan wrote:
A bag contains 3 white balls, 3 black balls & 2 red balls. One by one three balls are drawn out without replacement. What is the probability that the third ball is red?

A. 0.25
B. 0.15
C. 0.35
D. 0.45
E. 0.40

Thanks


The initial probability of drawing red ball is 2/8. Without knowing the other results, the probability of drawing red ball will not change for ANY successive drawing: second, third, fourth...

Similar problems:
ps-probability-gmat-made-me-lose-my-marbles-36830.html?hilit=initial%20draw
probability-of-picking-last-97015.html?hilit=initial%20probability
probability-question-please-solve-90272.html?hilit=initial%20probability#p686028

Hope it's clear.


!!!!!
went the long way - still under 2min

RedOtherRed +OtherRR+OOR

\(\frac{1}{28}+\frac{1}{28}+\frac{5}{28}=\frac{7}{28}=\frac{1}{4}\)
avatar
B
SagarV
Intern
Intern
Joined: 11 Jan 2021
Posts: 5
Re: A bag contains 3 white balls, 3 black balls & 2 red balls [#permalink] New post  26 Feb 2021, 09:45
Hello, please help me too:

As per my logic: P (last ball is Red) = 1 - P(First 2 balls are red)

= 1 - ( (2 / 8) * (1/7) )
= 1 - (1/28)
= 27 / 28
= 0.96

Where am I wrong ?
Thanks :)
avatar
S
Regor60
Manager
Manager
Joined: 21 Nov 2021
Posts: 141
Re: A bag contains 3 white balls, 3 black balls & 2 red balls [#permalink] New post  26 Apr 2022, 07:44
How many ways to arrange the 8 balls ?

8!/3!3!2! = 540 > Permutation eliminating duplicate colors

How many ways to arrange the balls where a red is in the third position ?

Arrange remaining 7 balls

7!/3!3! = 140

Probability 140/560 = 1/4

Posted from my mobile device
GMAT Club Bot
gmatclubot
Re: A bag contains 3 white balls, 3 black balls & 2 red balls [#permalink]
26 Apr 2022, 07:44
NEW TOPIC
POST REPLY
Downloads
My Bookmarks
Reviews
   1   2 
Moderators:
chetan2u
Math Expert
10505 posts
Bunuel
Math Expert
86356 posts
generis
Senior SC Moderator
5428 posts
yashikaaggarwal
Senior Moderator - Masters Forum
2893 posts

cron

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