>Here's an trick question: I make a round trip in an automobile between to points (let's call them "A" and "B"). I travel at an average speed of 40mph when going from point A to point B. On the return trip from B to A, I travel at an average speed of 60mph. What is the average speed for the entire round trip? (answer = 48mph)

Pretty neat. Had to pull out the old paper and pencil and the even older still functioning brain cell.