One solution to the truthteller-liar paradox uses two questions or statements. For example, a tourist in a city where half the residents are truthtellers and half are liars wants to go to the city zoo, but doesn't know which bus to take. The tourist, not knowing whether the bus driver is a truthteller or liar, can ask this question: "If I were to ask you if this bus will take me to the zoo, would you say 'yes'?"
Another form of the question is the following: "Of the two statements: 'You are a liar' and 'This bus will take me to the zoo' is only one of them true?"
Notice that each question makes certain assumptions about the bus driver's personality and understanding, not to mention present mood. What if the bus driver is having a bad day?