The boat and raft simultaneously moved along the river from the same point in the same direction.

The boat and raft simultaneously moved along the river from the same point in the same direction. Three quarters of an hour later, the distance between them became 450 meters. How fast was the boat moving if the sweat was moving at a speed of 3 km / h?

The boat and raft moved for 1/4 hour, which is equal to 15 minutes. The speed of the raft was 3 km / h = 3000m / 60 min = 50 m / min. In 15 minutes the raft sailed 50 * 15 = 750 (m). The boat sailed 450 m more, i.e. 750 + 450 = 1200 (m). This means that the speed with which the boat was moving is 1200: 15 = 80 (m / min).
Answer: 80 m / min