The boat covered the distance between the marinas in 3 hours, going at a speed of 20 km / h.

The boat covered the distance between the marinas in 3 hours, going at a speed of 20 km / h. On the way back, he reduced the speed by 5 km / h. How long it took the boat to make its way back.

Let’s determine how many kilometers a given boat covered when its speed was 20 km / h:

20 * 3 = 60.

Let’s determine the speed with which the boat sailed on the way back, knowing that it was 5 km / h less than before:

20 – 5 = 15.

Let’s determine how many hours it took for the boat to cover the same 60 kilometers with a reduced speed:

60/15 = 4.

Answer: The boat spent 4 hours on the way back.