The boat, which develops a speed of 22 km / h in still water, traveled 38 km against the current and 25 km

The boat, which develops a speed of 22 km / h in still water, traveled 38 km against the current and 25 km downstream, spending 3 hours for the entire journey. Find the speed of the river flow.

Let the speed of the river flow be x km / h, then:

22 + x (km / h) – speed of the boat downstream, since the boat develops a speed of 22 km / h in still water;

25: (22 + x) (h) – the time the boat was moving downstream, since it covered 25 kilometers downstream;

22 – х (km / h) – speed of the boat against the current;

38: (22 – x) (h) – the time of the boat’s movement against the current, since it covered 38 kilometers against the current.

Knowing that the boat spent 3 hours on the whole journey, we make the equation:

25: (22 + x) + 38: (22 – x) = 3;

3 ∙ x ^ 2 + 13 ∙ x – 66 = 0;

x₁ = – 22/3 – does not satisfy the condition of the problem;

х₂ = 3 km / h – speed of the river flow.

Answer: the speed of the river is 3 km / h.