How long does it take for the raft to sail 2.1 km along the river if the river flow velocity is 0.7 m / s?

Since the raft does not have its own speed, the speed of the raft will be equal to the speed of the river flow, that is, 0.7 m / s. To find out the time for which the raft will sail along the river 2.1 km = 2100 m at a river flow speed of 0.7 m / s, we use the formula: t = L / V, where L is the distance, V is the speed.
We have: t = 0.7 * 2100 = 1470 sec.