Tourists need to walk 40 km. The first four hours they walked at a speed of 5 km / h

Tourists need to walk 40 km. The first four hours they walked at a speed of 5 km / h, and the rest of the way at a speed of 4 km / h. How long did the tourists travel?

Let’s find the path traveled by tourists in the first four hours, knowing that they were walking at a speed of 5 km / h: 5 * 4 = 20 (km).
Let’s find the second part of the path, knowing that the total path is 40 km: 40 – 20 = 20 (km).
Let us find the time during which the tourists covered the second part of the journey: 20/4 = 5 (h).
Find the total travel time: 5 + 4 = 9 (h).
Answer: the tourists were on the road for 9 hours.