Yesterday’s Problem:
You are happily on your way to Truth City where it is well known that all the inhabitants always tell the truth. At one point in your travels you reach a fork in the road. One leg takes you to Truth City; the other leg takes you to Lies City which all the citizens always lie. The sign is very confusing – so you can not tell which fork takes you to Truth City.
A man stands near the sign, so you can ask him for directions. The problem of course is that you do now know whether the man is from Truth City (where everyone always tells the truth) or Lies City (where everyone always lies).
If you have time to ask this man one question and only one question, what can you ask him that will give you a 100% guarantee that you will get the information you need to take the fork which leads to Truth City?
Answer:
Ask the man: Which Way To Your Hometown?
If he is from Truth City he will point to the fork in the road that will take you to Truth City. If he is from Lies City, he will also point to the fork in the road that leads to Truth City (since people from Lies City always lie).
Today’s Problem:
There are three types of people in the city of Las Wages: those who always tell the truth; those who always lie and those who alternate between lying and truth telling.
If you meet an inhabitant on the streets of Las Wages and can ask only two questions, what two questions will enable to you determine what sort of a person he or she is?