6.4. Ivan on a tractor and Petr in a "Mercedes" left point A for point B. Petr arrived at point B, waited for 10 minutes, and called Ivan to find out that Ivan had only covered a third of the distance and was currently passing by a cafe. Petr drove to meet him. Not noticing Ivan, he reached the cafe and spent half an hour on a snack, then drove to point B. In the end, Petr arrived at point B at the same time as Ivan. How much time did Ivan spend on the entire journey, if both he and Petr traveled at constant speeds?
Solution. From the fact that Ivan had traveled a third of the distance by the time Peter had traveled the whole distance and waited for 10 minutes, we can conclude that by the time Ivan reaches point B, Peter could have traveled the route three times and waited for half an hour. Instead, he traveled the route $1+2 / 3+2 / 3=7 / 3$ times and waited for 40 minutes. This means that for Peter, $2 / 3$ of the journey in the first ratio is equivalent to 10 minutes of waiting in the second. From this, we can conclude that Peter takes 15 minutes to travel the entire route, and a third of Ivan's journey is 25 minutes. Therefore, Ivan's entire journey is 75 minutes.

Answer. 1 hour and 15 minutes.