The boat went 90 km downstream in some time, during the same time it would go against the current 70 km

The boat went 90 km downstream in some time, during the same time it would go against the current 70 km, what is the distance the raft is sailing during this time.

Let us determine to what number of kilometers the distance that the indicated vessel could overcome in the agreed time if it sailed in the reservoir without any current, knowing by the condition of the problem that it sailed 90 kilometers along the current of the water flow, and 70 kilometers against the current:

(70 + 90) / 2 = 80.

Let us determine how many kilometers the current added to the distance that this vessel covered when moving along the current of the water stream:

90 – 80 = 10.

Answer: The raft will swim 10 km.