Invite Hook #2

Ricardo's scheme worked beautifully; unfortunately the president was short-tempered, long-winded, and arrogant, but not a fool. He quickly figured out that Ricardo had to have been responsible. Initially he wanted to throw Ricardo to the lagoon's alligators, but his advisers persuaded him that on such an occasion it would be good to show mercy. Instead he decided to give Ricardo one of two fates: exile, or imprisonment until the president felt like letting him out (never).

The advisers pushed for the exile, but the president really wanted to throw the insolent boy in prison; however, he eventually agreed to let Ricardo decide his own fate.

Ricardo was placed in a room with two identical doors: guards were waiting behind one to take him to prison; behind the other was an escort waiting to see him off the island.

Inside the room were two men, one by each door. Both doorkeepers knew what was behind each door, and Ricardo was allowed to ask one of them a single question. As Ricardo had been informed, one had been instructed to lie, the other to tell the truth.

How can Ricardo determine, with a single yes/no question, which door he should go through for the life of exile?

Solution