From the text: In one of my many experiments with numbers I found an interesting property which I will describe in everyday terms before going into a more formal analysis. Imagine a circular putting green on a golf course. A golfer wants to practice putting from the edge of the green. He therefore drops a large number of golf balls on the very edge of the green. He then stands on the edge of the green and is struck by the thought What might be the average distance from here to all these golf balls? We measure with the radius of the green as unit and consider the diameter of a golf ball as negligible. The amazing result is that: the average distance is $A\sim π/4$.