GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 13 Dec 2019, 14:23

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

Probability Ques

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

Hide Tags

Find Similar Topics 
Intern
Intern
avatar
B
Joined: 30 Jun 2019
Posts: 46
Probability Ques  [#permalink]

Show Tags

New post 23 Nov 2019, 09:35
Hey Guys


What can be the quickest approach to this question:-

A bag contains 3 Blue 5 Green 4 yellow balls
3 balls are drawn at random without replacement. What is the probability that exactly 2 of the 3 balls will be Blue.?

The approach i used is very lengthy and I think not correct or advisable

I used 1-(Prob of All Blue + Prob of no Blue + Prob of One Green)

Thanks

Posted from my mobile device
Math Expert
avatar
V
Joined: 02 Aug 2009
Posts: 8310
Re: Probability Ques  [#permalink]

Show Tags

New post 23 Nov 2019, 22:38
Sam10smart wrote:
Hey Guys


What can be the quickest approach to this question:-

A bag contains 3 Blue 5 Green 4 yellow balls
3 balls are drawn at random without replacement. What is the probability that exactly 2 of the 3 balls will be Blue.?

The approach i used is very lengthy and I think not correct or advisable

I used 1-(Prob of All Blue + Prob of no Blue + Prob of One Green)

Thanks

Posted from my mobile device


The correct way would be
Ways in which 2 are blue 3C2 and the third could be any of 5+4 or 9..3C2*9C1=3*9=27
Total ways = (3+5+4)C3=12C3=12*11*10/3*2=220

Prob=27/220
_________________
Intern
Intern
avatar
B
Joined: 30 Jun 2019
Posts: 46
Re: Probability Ques  [#permalink]

Show Tags

New post 23 Nov 2019, 22:56
chetan2u wrote:
Sam10smart wrote:
Hey Guys


What can be the quickest approach to this question:-

A bag contains 3 Blue 5 Green 4 yellow balls
3 balls are drawn at random without replacement. What is the probability that exactly 2 of the 3 balls will be Blue.?

The approach i used is very lengthy and I think not correct or advisable

I used 1-(Prob of All Blue + Prob of no Blue + Prob of One Green)

Thanks

Posted from my mobile device


The correct way would be
Ways in which 2 are blue 3C2 and the third could be any of 5+4 or 9..3C2*9C1=3*9=27
Total ways = (3+5+4)C3=12C3=12*11*10/3*2=220

Prob=27/220


Dear Sir

Thank you so much.

Can you also try and get the same result using my approach?

Thanks
Math Expert
avatar
V
Joined: 02 Aug 2009
Posts: 8310
Re: Probability Ques  [#permalink]

Show Tags

New post 23 Nov 2019, 23:11
Sam10smart wrote:
chetan2u wrote:
Sam10smart wrote:
Hey Guys


What can be the quickest approach to this question:-

A bag contains 3 Blue 5 Green 4 yellow balls
3 balls are drawn at random without replacement. What is the probability that exactly 2 of the 3 balls will be Blue.?

The approach i used is very lengthy and I think not correct or advisable

I used 1-(Prob of All Blue + Prob of no Blue + Prob of One Green)

Thanks

Posted from my mobile device


The correct way would be
Ways in which 2 are blue 3C2 and the third could be any of 5+4 or 9..3C2*9C1=3*9=27
Total ways = (3+5+4)C3=12C3=12*11*10/3*2=220

Prob=27/220


Dear Sir

Thank you so much.

Can you also try and get the same result using my approach?

Thanks


So probability of all blue =3C3/12C3=1/220
Probability of one blue = 3C1*9C2/12C3=3*36/220=108/220
Probability of none blue =9C3/12C3=84/220
Total ways =1-(1/220+108/220+84/220)=1-(1+108+84)/220=1-193/220=27/220
_________________
Intern
Intern
avatar
B
Joined: 30 Jun 2019
Posts: 46
Re: Probability Ques  [#permalink]

Show Tags

New post 23 Nov 2019, 23:30
chetan2u thanks alot!!

Posted from my mobile device
GMAT Club Bot
Re: Probability Ques   [#permalink] 23 Nov 2019, 23:30
Display posts from previous: Sort by

Probability Ques

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





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