very hard prob question for gmat

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 96
Joined: Fri Apr 23, 2010 1:14 am
Thanked: 1 times
Followed by:1 members

very hard prob question for gmat

by quantskillsgmat » Wed Dec 14, 2011 12:32 am
If we have an empty room, and every week there is a 0.6 probability for a person to join, 0.2 probability for a person to leave, and 0.2 probability for no change (only one action can be performed per week), what is the probability that there are at least 40 people in the room after 104 weeks?

(A) 0.42
(B) 0.55
(C) 0.61
(D) 0.67
(E) 0.74
Source: — Problem Solving |

User avatar
Legendary Member
Posts: 588
Joined: Sun Oct 16, 2011 9:42 am
Location: New Delhi, India
Thanked: 130 times
Followed by:9 members
GMAT Score:720

by rijul007 » Wed Dec 14, 2011 1:03 am
This qn is tooooo lengthy
Out of scope for GMAT