Martin Gardner died last Saturday at the age of 95. He was probably best known for his publications related to recreational mathematics.
In his memory:
A commuter is in the habit of arriving at his suburban station each evening exactly at five o’clock. His wife always meets the train and drives him home. One day he takes an earlier train, arriving at the station at four. The weather is pleasant, so instead of telephoning home he starts walking along the route always taken by his wife. They meet somewhere on the way. He gets into the car and they drive home, arriving at their house ten minutes earlier than usual. Assuming that the wife always drives at a constant speed, and that on this occasion she left just in time to meet the five o’clock train, at what time was the husband picked up? (Source: The Scientific American Book of Mathematical Puzzles and Diversions by Martin Gardner, Simon and Schuster, NY, 1959. p. 26. This book also has an excellent chapter on hexaflexagons.)