BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

probability medium diff. (600-650)

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 1337
Joined: Sat Dec 27, 2008 6:29 pm
Thanked: 127 times
Followed by:10 members

probability medium diff. (600-650)

by Night reader » Thu Dec 02, 2010 12:07 pm
From a group of 3 sophomores and 3 juniors, 4 students are to be randomly selected. What is the probability that more juniors than sophomores will be selected?

(A) 1/10
(B) 1/6
(C) 1/5
(D) 1/4
(E) 1/3
My knowledge frontiers came to evolve the GMATPill's methods - the credited study means to boost the Verbal competence. I really like their videos, especially for RC, CR and SC. You do check their study methods at https://www.gmatpill.com
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pm
Location: Milpitas, CA
Thanked: 447 times
Followed by:88 members

by Rahul@gurome » Thu Dec 02, 2010 12:13 pm
Night reader wrote:From a group of 3 sophomores and 3 juniors, 4 students are to be randomly selected. What is the probability that more juniors than sophomores will be selected?

(A) 1/10
(B) 1/6
(C) 1/5
(D) 1/4
(E) 1/3
Total number of ways to select 4 students from 6 = 6C4 = 15

Possible selection such that more juniors than sophomores are selected,
  • 3 junior, 1 sophomore
    1 sophomore out of 3 can be selected in 3 ways.
    Thus total 3 possible selections
Required probability = 3/15 = 1/5

The correct answer is C.
Last edited by Rahul@gurome on Thu Dec 02, 2010 12:17 pm, edited 1 time in total.
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
User avatar
Community Manager
Posts: 991
Joined: Thu Sep 23, 2010 6:19 am
Location: Bangalore, India
Thanked: 146 times
Followed by:24 members

by shovan85 » Thu Dec 02, 2010 12:14 pm
Night reader wrote:From a group of 3 sophomores and 3 juniors, 4 students are to be randomly selected. What is the probability that more juniors than sophomores will be selected?

(A) 1/10
(B) 1/6
(C) 1/5
(D) 1/4
(E) 1/3
4 students are to be randomly selected in C(6,4) = 15 ways

More juniors to be seleted then 3 Juniors 1 sophomore is the only possibility.

1 S can be selected in C(3,1) = 3 ways and 3 J can be selected in C(3,3) = 1 ways

Thus 3*1/15 = 1/5

IMO C
If the problem is Easy Respect it, if the problem is tough Attack it
Top
Post new topic Post Reply
• Page 1 of 1