The distance between the marinas is 45 km. The boat covered five-twelfths of this distance in 1.2

The distance between the marinas is 45 km. The boat covered five-twelfths of this distance in 1.2 hours; the rest of the way the boat covered the speed of 21 km / h. How long did the boat take all the way?

According to the condition of the problem, in 1.2 hours the boat covered the distance:

45 * 5/12 = 225/12 = 18.75 (km).

Therefore, it remains for him to go through:

45 – 18.75 = 26.25 (km).

Since this distance the boat went at a speed of 21 km / h, it took time:

26.25: 21 = 1.25 hours.

Thus, the boat spent time on the whole journey:

1.2 + 1.25 = 2.45 hours.

Answer: 2.45 hours.