Friday Puzzler -- Early Quitting time
alexy
Bob drives from home to pick up his wife, Sally, at quitting time every day, and they get home at exactly 6:00 pm. One day, Sally gets off work 1/2 hour early. Since it is a nice day, she decides not to call Bob, but just to walk toward home along the same route they drive. Bob leaves at the normal time to pick her up, sees her walking, picks her up, and they return home. They get home at 5:50. How long did Sally walk?
The route Bob takes is the same each direction, and is symmetrical, in the sense that if there is a stretch where he drives 25mph coming in to pick Sally up, they will drive that same stretch of road at 25mph going home. His car is one of those special models that make instantaneous u-turns.