Find the speed of the river if the boat covered 96.5 km in 5 hours and 81.6 km upstream in 4.8 hours.

It is more convenient to solve this problem using an equation. Let the speed of the current x km / h, and the speed of the boat – y km / h. Then the speed downstream is x + y km / h, and the distance covered in 5 hours:
5 * (x + y) = 96.5.
x + y = 19.3.
Since the speed against the current is y – x km / h, therefore the distance traveled:
4.8 * (y – x) = 81.6.
y – x = 17.
y = 17 + x.
Substitute y in the first equation:
17 + x + x = 19.3.
17 + 2 * x = 19.3.
2 * x = 2.3.
x = 1.15.
Answer: current speed: 1.15 km / h.