Question
A speaks the truth 4 out of 7 times and B speaks truth 8 out of 9 times. What is the probability that they contradict each other in stating the same fact?
Solution
P (A truth) = Probability that A speaks the truth =4/7 P (A lie) = Probability that A lies = 1 - P (A truth) =1-4/7 =3/7 P (B Truth) = Probability that B speaks the truth = 8/9 P (B lie) = Probability that B lies = 1- P (B truth) = 1-8/9 =1/9. 
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