Ram singh goes to his office in the city every day from his suburban house. His driverMangaram drops him at the railway station in the morning and picks him up in the evening.Every evening Ram singh reaches the station at 5 o'clock. Mangaram also reaches at thesame time. One day Ram singh started early from his office and came to the station at 4o'clock. Not wanting to wait for the car he starts walking home. Mangaram starts at normaltime, picks him up on the way and takes him back house, half an hour early. How much timedid Ram singh walked?