THIS MONTH'S QUIZ
Smith and Jones are both somewhat untruthful, and one out of every three statements they make is a lie, i.e. it does not agree with the truth or what they have been told is the truth. Smith, moreover, is not noted for his punctuality, and only on one day in every four does he leave home early enough to walk to the office, having to travel by bus on the other three.
One morning Smith told Jones whether he had walked that day, and Jones passed the news on to me.
1. What is the probability that Jones tells me Smith has walked?
2. If Jones tells me Smith has walked, what is the probability that he had, in fact, done so?
3. What is the probability that what Jones tells me about Smith's journey is true?