回复：儿子拿回来的题, 搞不出了, 请大家帮忙

Let A1 is the event P1 working, and so on...., P(Ai)=0.5,
then
P(AB)=P[A1A2UA5A2UA5A3UA4A3]
=P(A1A2)+P(A5A2)+P(A5A3)+P(A4A3)-P(A1A2A5A2)-P(A1A2A5A3)-P(A1A2A4A3)-P(A5A2A5A3)-P(A5A2A4A3)-P(A1A2A4A3)
+P(A1A2A5A2A5A3)+P(A1A2A5A2A4A3)+P(A1A2A5A3A4A3)+P(A5A2A5A3A4A3)-P(A1A2A5A2A5A3A4A3)
=1/4+1/4+1/4+1/4-1/8-1/16-1/16-1/8-1/16-1/8+1/8+1/16+1/16+1/8-1/32
=25/32.
So the answer is 25/32

所有跟帖： 

• 回复：回复：儿子拿回来的题, 搞不出了, 请大家帮忙 -tony_ren- ♂ (74 bytes) () 07/03/2010 postreply 20:25:31

• your formula are good,but opperation is.... -jinjing- ♀ (164 bytes) () 07/04/2010 postreply 15:07:20

• 回复：Still not correct, but thanks.... -tony_ren- ♂ (117 bytes) () 07/04/2010 postreply 19:19:37

• P(A5A2A5A3A4A3)=1/16 ,it is not 1/8,last term is-1/32 -jinjing- ♀ (23 bytes) () 07/05/2010 postreply 07:30:05