The average speed
A man is walking down a street along which runs a streetcar line. He notices that, for every 40 streetcars which pass him traveling in the same direction as he, 60 pass in the opposite direction. If the man’s walking speed is 3 miles per hour, what is the average speed of the streetcars?
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15 miles per hour.
The engineering department was arranging for a rather expensive catered lunch to bid farewell to their retiring colleague. They calculated that it would cost each person $30. One good mathematician remarked, "It's lucky that there aren't five fewer of us to split the...