A secretary of a cooperative in a lowland area, Mr. János, travels to Budapest weekly. His wife gets in the car at 4 o'clock and meets the train at the station, and by 5 o'clock they are home. One day, the train arrived earlier, but the wife did not know this, so she met her husband on the way home. They arrived home 10 minutes before 5 o'clock. How far did Mr. János walk, if his wife drives at an average speed of $42 \mathrm{~km}$ per hour?
János landlord's wife still had to drive for five more minutes to reach the station. Therefore, János landlord walked as much as the car would cover in 5 minutes, which is $\frac{42}{12}=3.5 \mathrm{~km}$.