How Long Walking

A chauffeur always arrives at the train station at five o'clock sharp to pick up his boss and drive him home. One day, the boss arrives an hour early, starts walking home, and is eventually picked up. He is home 20 minutes earlier than usual. How long did the boss walk before he was picked up by the chauffeur?

Answer:

As the chauffeur's round trip was 20 min. shorter, he picked up his boss 10 min. before 5:00. The boss walked 50 minutes.