There are three playing cards lying face up, side by side.  A five is just to the right of a two.  A five is just to the left of a two.  A spade is just to the left of a club, and a spade is just to the right of a spade.

What are the three cards?

You are in the dark, and on the floor there are six shoes of three colors, and a heap of twenty-four socks, black and brown.  How many socks and shoes must you take into the light to be certain that you have a matching pair of socks and a matching pair of shoes?

A milkman has two empty jugs: a three gallon jug and a five gallon jug.  How can he measure exactly one gallon without wasting any milk?