Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 25 Apr 2015, 23:22

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A certain junior class has 1000 students and a certain

Author Message
TAGS:
Intern
Joined: 07 Mar 2005
Posts: 25
Location: USA
Followers: 0

Kudos [?]: 0 [0], given: 0

A certain junior class has 1000 students and a certain [#permalink]  14 Apr 2006, 18:36
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?
- 3/40,000
- 1/3600
- 9/2000
- 1/60
- 1/15
VP
Joined: 29 Dec 2005
Posts: 1349
Followers: 7

Kudos [?]: 30 [0], given: 0

Re: Prob Q (GMATPrep) [#permalink]  14 Apr 2006, 18:52
ashkapoo wrote:
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?
- 3/40,000
- 1/3600
- 9/2000
- 1/60
- 1/15

p (sibling) = (60/1,000) (1/800) = 3/40,000
Intern
Joined: 07 Mar 2005
Posts: 25
Location: USA
Followers: 0

Kudos [?]: 0 [0], given: 0

Would'nt it be (60/1,000)*(1/800) + (60/800)*(1/1,000), depending on whether you pick a senior or junior first?
VP
Joined: 29 Dec 2005
Posts: 1349
Followers: 7

Kudos [?]: 30 [0], given: 0

ashkapoo wrote:
Would'nt it be (60/1,000)*(1/800) + (60/800)*(1/1,000), depending on whether you pick a senior or junior first?

because thre are equal junier and sinior siblings in each class.

(60/1,000)*(1/800) or (60/800)*(1/1,000) are same.

you have 60 chances out of either 1000 or 800 to get a sibling from either sinior or junior. then you go to next, which could be either...
Similar topics Replies Last post
Similar
Topics:
A certain junior class has 1000 students and a certain 1 04 Aug 2008, 06:11
A certain junior class has 1000 students and a certain 3 07 Jul 2008, 19:59
A certain junior class has 1000 students and a certain 1 20 May 2006, 04:45
A certain junior class has 1000 students and a certain 1 07 May 2006, 17:04
A certain junior class has 1000 students and a certain 3 19 Feb 2006, 12:58
Display posts from previous: Sort by