Find the speed of the river if the motor boat passed 9 m across the lake in 30 minutes, and after entering

Find the speed of the river if the motor boat passed 9 m across the lake in 30 minutes, and after entering the river, covered 28 km in 2 hours. The boat engine worked steadily throughout the entire trip.

We convert time from minutes to hours.

30 minutes = 30/60 = 1/2 hour.

Find your own speed of the motor boat.

Divide the distance covered by the time.

9/1/2 = 9 * 2 = 18 km / h.

We find the speed of the boat against the stream of the river.

Divide 28 km by a known time.

28/2 = 14 km / h.

Find the speed of the river.

To do this, we subtract its speed when moving along the river from its own speed of the motor boat.

Will be:

18 – 14 = 4 km / h.

Answer: The speed of the river is 4 km / h.