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

It is currently 21 Sep 2018, 16:36

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

A certain junior class has 1000 students and a certain

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 12 May 2005
Posts: 29
GMAT ToolKit User
A certain junior class has 1000 students and a certain  [#permalink]

Show Tags

New post 05 Jan 2008, 14:23
1
1
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

89% (00:59) correct 11% (01:02) wrong based on 74 sessions

HideShow timer Statistics

A certain junior class has 1000 students and a certain senior class has 800 students. Among these students, there are 60 sibling pairs, each consisting of 1 junior and 1 senior.If 1 student is to be selected at random from each class, what is the probability that the 2 students selected will be a sibling pair?
A: 3/40000
B: 1/3600
C:9/2000
D: 1/60
E:1/15
OA is A.
Can someone please explain this problem in detail?
Logic says since there are 60 sibling pairs:
There are 30 seniors and 30 juniors
So probability is p= 30/1000* 30/800.
Why is this wrong?

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.


If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Intern
Intern
avatar
Joined: 25 Sep 2007
Posts: 22
Re: Probability  [#permalink]

Show Tags

New post 05 Jan 2008, 14:41
60 pairs of siblings = 120 people; 60 juniors and 60 seniors; Probability of selecting a junior out of the class of 1000 people is 60/1000. Probability of selecting his/her sibling out of the class of seniors is 1/800 (since only one person can be his/her sibling);

So we have 60/1000 * 1/800 = 3/40000
Intern
Intern
avatar
Joined: 12 May 2005
Posts: 29
GMAT ToolKit User
Re: Probability  [#permalink]

Show Tags

New post 05 Jan 2008, 14:46
Oops. I got the question wrong then. Thanks that makes sense.
Manager
Manager
avatar
Joined: 27 Oct 2008
Posts: 180
Re: Probability  [#permalink]

Show Tags

New post 27 Sep 2009, 10:54
A certain junior class has 1000 students and a certain senior class has 800 students. Among these students, there are 60 sibling pairs, each consisting of 1 junior and 1 senior.If 1 student is to be selected at random from each class, what is the probability that the 2 students selected will be a sibling pair?
A: 3/40000
B: 1/3600
C:9/2000
D: 1/60
E:1/15

Soln: Total no. of ways of choosing two people, one from each class is 800 * 1000.
Of these total outcomes, there are only 60 pairs which are sibling pairs. Hence answer is
= 60/(800 * 1000)
= 3/40000

ans is A
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 8131
Premium Member
Re: A certain junior class has 1000 students and a certain  [#permalink]

Show Tags

New post 14 Oct 2017, 09:52
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.


If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: A certain junior class has 1000 students and a certain &nbs [#permalink] 14 Oct 2017, 09:52
Display posts from previous: Sort by

A certain junior class has 1000 students and a certain

  post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


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®.