The speed of the boat along the river is 9 km / h. The speed of the river is 3 km / h. How long will it take

The speed of the boat along the river is 9 km / h. The speed of the river is 3 km / h. How long will it take for this boat to sail 27 km along the river and return?

1) Calculate the boat’s own speed:

9 – 3 = 6 km / h.

2) Let’s calculate the speed of the boat against the current of the river:

6 – 3 = 3 km / h.

3) Let’s calculate the time it takes for the boat to sail 27 km along the river:

27: 6 = 4.5 hours.

4) Let’s calculate the time it takes for the boat to sail 27 km against the river flow:

27: 3 = 9 hours.

5) Let’s calculate the time it takes for the boat to sail 27 km along the river and come back:

4.5 + 9 = 13.5 hours.

Answer: in 13.5 hours.