In a long, narrow chute there are 8 balls: 4 black ones on the left, and 4 white ones-slightly larger-on the right. In the middle of the chute there is a small niche that can hold 1 ball of either color. The chute’s right end has an opening large enough for a black but not a white ball.

Roll all the black balls out of the chute. You can’t pick them up from the chute.

A detachment of soldiers must cross a river. The bridge is broken, the river is deep. Suddenly the officer in charge spots 2 boys playing in a rowboat by the shore. The boat is so tiny, however, that it can only hold 2 boys or 1 soldier.

Still, all the soldiers succeed in crossing the river in the boat. How?

How many cats are in a small room if in each of the four corners a cat is sitting, and opposite each cat there sit 3 cats, and at each cat’s tail a cat is sitting?

You’re in a mansion and the power is out. You see some signs on three doors. One says, “Death from drowning,” another says “Death from machine guns,” and the last one says “Death from electric chair.” Then you see another big sign off to the side that says “Or stay in the mansion and starve to death.” What do you choose and still live?