TestMagic Forums - View Single Post - Help on an extrmelye difficult probability question

cambridgedove · 2009 January 16th, 05:45 PM

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

Please explain how you do it, thanks!

2009 January 16th, 05:45 PM	#1 (permalink)
cambridgedove Within my grasp! Join Date: Jan 2009 Posts: 148	Help on an extrmelye difficult probability question 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 Please explain how you do it, thanks!