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

It is currently 18 Oct 2018, 04:35

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

Help with a question in combinatorics

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

Hide Tags

Intern
Intern
avatar
B
Joined: 17 May 2018
Posts: 15
CAT Tests
Help with a question in combinatorics  [#permalink]

Show Tags

New post 28 Sep 2018, 01:20
Hello, would much appreciate help with this kind of question :

there are 3 baskets, each with 5 balls.
in first basket we have 4 black balls, 1 yellow.
in second we have 3 black balls, 2 yellow.
in third we have 2 black , 3 yellow.
we pick one ball from each basket. what is the probability that we get at least one black ball ?

thanks
Manager
Manager
avatar
S
Joined: 23 Nov 2017
Posts: 97
Location: Singapore
Concentration: Strategy, Other
GMAT 1: 660 Q49 V33
Re: Help with a question in combinatorics  [#permalink]

Show Tags

New post 28 Sep 2018, 01:28
Somnium wrote:
Hello, would much appreciate help with this kind of question :

there are 3 baskets, each with 5 balls.
in first basket we have 4 black balls, 1 yellow.
in second we have 3 black balls, 2 yellow.
in third we have 2 black , 3 yellow.
we pick one ball from each basket. what is the probability that we get at least one black ball ?

thanks



Is the answer 119/125 ?
Senior Manager
Senior Manager
avatar
S
Joined: 19 Oct 2013
Posts: 267
Location: Kuwait
GPA: 3.2
WE: Engineering (Real Estate)
GMAT ToolKit User
Re: Help with a question in combinatorics  [#permalink]

Show Tags

New post 28 Sep 2018, 01:43
Somnium wrote:
Hello, would much appreciate help with this kind of question :

there are 3 baskets, each with 5 balls.
in first basket we have 4 black balls, 1 yellow.
in second we have 3 black balls, 2 yellow.
in third we have 2 black , 3 yellow.
we pick one ball from each basket. what is the probability that we get at least one black ball ?

thanks


Happen to have the answer choices? What is the source for this question?
Intern
Intern
avatar
B
Joined: 17 May 2018
Posts: 15
CAT Tests
Help with a question in combinatorics  [#permalink]

Show Tags

New post 28 Sep 2018, 03:33
in one of official CATs , but unfortunately I don't remember the exact data that was there so I don't know what the answer should be. I changed the stats a bit..
Manhattan Prep Instructor
User avatar
G
Joined: 04 Dec 2015
Posts: 629
GMAT 1: 790 Q51 V49
GRE 1: Q170 V170
Re: Help with a question in combinatorics  [#permalink]

Show Tags

New post 01 Oct 2018, 12:20
1
Somnium wrote:
Hello, would much appreciate help with this kind of question :

there are 3 baskets, each with 5 balls.
in first basket we have 4 black balls, 1 yellow.
in second we have 3 black balls, 2 yellow.
in third we have 2 black , 3 yellow.
we pick one ball from each basket. what is the probability that we get at least one black ball ?

thanks


If you see language like 'at least one' in a probability problem, this strategy will usually work. Instead of finding the probability of getting one black ball, then two black balls, then three black balls, you can actually just find the probability of getting all yellow balls, and subtract from 1. You can do that because you're basically looking for the probability that anything other than all yellow is what happens. That'll be the 'opposite' of the probability that you get all yellow.

The probability of getting all yellow balls is 1/5 * 2/5 * 3/5 (the product of the probability of getting a yellow ball from each basket). That equals 6/125.

So, the probability of getting at least one black (in other words, NOT getting all yellow) is 1-6/125 or 119/125.
_________________

Image

Chelsey Cooley | Manhattan Prep Instructor | Seattle and Online

My upcoming GMAT trial classes | GMAT blog archive

GMAT Club Bot
Re: Help with a question in combinatorics &nbs [#permalink] 01 Oct 2018, 12:20
Display posts from previous: Sort by

Help with a question in combinatorics

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.