You are lost in the woods. You come to a T-junction and are wondering which way to go. You have a funny feeling that one way will get you out, the other will mean certain death. Weird, eh?
Wizard of Oz approaches you. “A left turn will get you out of the woods,” he advises. Nearby, Chris hears this and calls out, “Beware of him. He lies!” “Exactly 4 times out of 10, I do!” Wiz retorts, and disappears.
You know from experience that Chris always tell the truth. You also know that throughout his life, Wiz tells the truth a certain number of sentences out of ten, determined by chance at birth. You also know this number is an integer. Which way should you turn to maximise your chance of escape?
Chris won’t sleep tonight!