A man is imprisoned in a ten-foot by ten-foot by ten-foot room. The walls are made of concrete, the floor is made out of dirt, and the only openings are a locked door and a skylight ...

You have a delicious round birthday cake. How many equal-sized pieces can you cut the cake into by making only three straight slices with a knife and without moving any of the pieces?

You are in an empty room with a glass of water. The glass is a right cylinder that looks like it is about half-full, but you are not quite sure ...