One of the best brain teasers and riddles goes as follows:
There are three switches downstairs. Each corresponds to one of the three light bulbs in the attic. You can turn the switches on and off and leave them in any position.
How would you identify which switch corresponds to which light bulb, if you are only allowed one trip upstairs?
You are shown two doors – one leading to hell and the second one to heaven and only the door guards know what is behind the doors. One guard is always lying and the other is always telling the truth (of course, you don’t know who is lying). You can ask only one guard one question.
A fellow encountered a bear in a wasteland. Both got frightened – fellow ran to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear.
Three missionaries and three cannibals want to get to the other side of a river. There is a small boat, which can fit only two. To prevent a tragedy, there can never be more cannibals than missionaries together.
