In 4 hours, the boat travels with the stream 2.4 times more than in 2 hours against the stream

In 4 hours, the boat travels with the stream 2.4 times more than in 2 hours against the stream. What is the speed of a boat in still water if the current speed is 1.5 km / h?

1. We take as x the distance that the boat sails in one hour, excluding the river flow.

2. Speed of the boat when moving down the river (x + 1.5), up the river (x – 1.5).

3. We make the equation:

4 (x + 1.5): 2 (x – 1.5) = 2.4;

4x + 6 = 4.8x – 7.2;

0.8x = 13.2;

x = 16.5;

Answer: the boat sails in one hour without taking into account the river flow 16.5 km.