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 speed of the boat.

Suppose that the boat’s own speed is x km / h, and the river speed is y km / h.

Therefore, we can write the problem conditions in the form of a system of two equations with two unknowns:

(x + y) * 1 1/3 = 24,

(x – y) * 1.5 = 24 – 3.

From the first equation we get:

(x + y) * 4/3 = 24,

(x + y) / 3 = 6,

x + y = 18,

x = 18 – y.

Substitute the resulting x value into the second equation:

(18 – y – y) * 1.5 = 21,

18 – 2 * y = 14,

2 * y = 4,

y = 2.

Since the speed of the river is 2 km / h, the boat’s own speed is 18 – 2 = 16 km / h.