The boat covered 72 km along the river and came back which way took him more

The boat covered 72 km along the river and came back which way took him more time and how much if the boat’s own speed is 21 km / h, the speed of the river is 3 km / h.

1. We calculate the speed of a river vessel in the direction of the flow of water in the river:

21 + 3 = 24 km / h.

2. We calculate the speed of a river vessel against the flow of water in the river:

21 – 3 = 18 km / h.

3. In the direction of the water flow in the river, the river vessel sailed:

72: 24 = 3 hours.

4. In the opposite direction, the river vessel sailed:

72: 18 = 4 hours.

5. We calculate how many hours longer a river vessel sailed against the flow of water in the river than along the river:

4 – 3 = 1 hour.

Answer: the path upstream of the river is 1 hour longer than downstream.