The boat covered 54 km across the lake in 3 hours, and 60 km along the river in another 3 hours.

The boat covered 54 km across the lake in 3 hours, and 60 km along the river in another 3 hours. Determine the speed of the river.

There is no current in the lake.

First, let’s determine the boat’s own speed by dividing the number of kilometers traveled by the boat on the lake by the amount of time it took for this:

1) 54 km / 3 h = 18 km / h.

Similarly, we will determine the speed of the boat behind the current along the river:

2) 60 km / 3 h = 20 km / h.

Further, we subtract the boat’s own speed from the speed of the boat behind the current, then we find out the speed of the river flow:

3) 20 km / h – 18 km / h = 2 km / h.

Bottom line: the speed of the river is two kilometers in one hour.