If the speed of the motor boat along the river is 18.4 km / h, and against the current 12.8

If the speed of the motor boat along the river is 18.4 km / h, and against the current 12.8 km / h, then the speed of the river is …

1. Let the speed of the boat in the river without the current v, and the speed of the river current x.

2. We write down the speed of the boat downstream as v + x = 18.4 km / h.

3. We write down the speed of the boat against the current as v – x = 12.8 km / h.

4. Find the difference between the speed upstream and upstream and express from this x.

v + x – (v – x) = 18.4-12.8;

v + x – v + x = 5.6;

2 * x = 5.6;

x = 2.8 km / h.

Answer: the speed of the river is 2.8 km / h.