Question
Axe speaks truth only when Wye does not speak truth,
then what is the probability that Zed does not speak truth on a question? There are three people – Axe, Wye and Zed. Probability that Axe speaks the truth is 7/20, probability that Wye speaks the truth is 3/5 and probability that Zed speaks truth is 5/6. For a particular question asked, at most 2 people speak truth. All people answer to a particular question asked.Solution
Case (1) : Wye does not speak truth So, Axe speaks truth here Probability that Zed does not speaks truth = 7/20 ×(1-3/5)×(1-5/6) = 7/300 Case (2) : Wye speaks truth So, Axe does not speaks truth here Probability that Zed does not speaks truth = (1-7/20)× 3/5 ×(1-5/6) = 13/200 Required Probability = 7/300+ 13/200 = 53/600