Question

A bag contains four balls. two balls are drawn at random and found to be white. what is the probability that all balls are white

Answer 1

E1 be the event only two balls are white
E2​ be the event 3 balls are white 
E3 be the event 4 balls are white 
p(e1)=p(e2)=p(e3)= 1/3
A be the event drawn balls both are white
we have to find p(E3/A)
p(A/E1)=2/4*1/3=1/6
p(A/E2)=3/4*2/3=1/2
p(A/E/3)=4/4=1
p(E3/A)= 1/3*1/(1/3*1/6+1/3*1/2+1/3*1) => 3/5