A Logic Puzzle

Most readers are probably familiar with the old chestnut of two doors and two guards, one of which always tells the truth and one of which always lies. But what about if we have three guards?

This is a twist on the classic puzzle that I found pleasantly appealing. Without further ado:

A prisoner is given a choice between two doors; one of which leads to freedom and the other of which leads to certain death. In front of the doors stand three guards, one of whom always tells the truth, one of whom always lies and the other of which answers randomly. The guards will only answer ‘yes’ or ‘no’ to questions. The prisoner does not know which guard is which.

In only two questions, how does the prisoner find out which door is safe?



Answers will be revealed later this week. The answers can be found elsewhere on the internet, so if you wish to solve yourself, avoid googling.