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May 14th, 2014, 11:43 AM  #1 
Newbie Joined: May 2014 From: england Posts: 11 Thanks: 0  independent events rule question  please please help as exam tomorrow!
For 2 independent events, A and B, p(AuB')=0.7 and P(A)=0.5. A and B are independent. Find the probability of event B happening.? I do not understand this question, sorry. The markscheme working is (0.3+x)0.5=x 0.15 = 0.5x x=0.3 p(B)=0.6 if this is the independent events rule, where does b being 0.3+x come from please? id really appreciate a stepbystep response thanks! 
May 14th, 2014, 12:52 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,807 Thanks: 717 
I don't where the formula came from. My approach: P(A∪B') = P(A) + P(B')  P(A∩B') P(A∩B') = P(A)P(B') (independence) Let x = P(B') .7 = .5 + x  .5x x = .4 P(B) = 1x = .6 
May 15th, 2014, 01:25 AM  #3 
Newbie Joined: May 2014 From: england Posts: 11 Thanks: 0  thanks
thanks a lot! understood 

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