The boat sails 24 km along the river in 1 hour 20 minutes, and 3 km less against the current in 1.5 hours.

The boat sails 24 km along the river in 1 hour 20 minutes, and 3 km less against the current in 1.5 hours. Find the speed of the river and your own boat speed.

To solve the problem, it is necessary to compose a system of equations in which we write the own speed of the boat as x.
in this case, the speed of the river flow y.
We write down the travel time along the river as 1 1/3.
We get.
24/4/3 = x + y.
21 / 1.5 = x – y.

24 * 3/4 = x + y.
18 = x + y.
14 = x – y.
Let us express x from the first equation.
x = 18-y.
Substitute the x value in the second equation.
14 = 18 – y – y.
2 * y = 4.
y = 4/2 = 2 km / h River flow speed.
Find the boat’s own speed.
x = 18 – 2 = 16 km / h.