Re: DSE 2013 Doubts

Posted by Akshay Jain on May 30, 2014; 2:30pm
URL: http://discussion-forum.276.s1.nabble.com/DSE-2013-Doubts-tp7590991p7591100.html

prob that a letter is from male=1/2=prob that it is from a female
P(event A)=prob that both letters are from female=1/2*1/2=1/4
P(event B)=prob that 1st letter is from female and 2nd is from a male=1/2*1/2=1/4
P(event C)=prob that 1st letter is from male and 2nd is from a female=1/2*1/2=1/4
but the above event C shud be included in event B because no matter in what order the postman gets the letter he will deliver female letter 1st whenever he has a letter from a female
given that 1st letter is from a female
prob that 2nd letter is also from a female is (1/4)/[(1/4)+(1/2)]=1/3