Answer:
of the distance
Explanation:
We know that a ferry traveled
of the distance between two ports in
hours.
In order to calculate what fraction of the distance between the two ports can the ferry travel in one hour we can do the following reasoning :
The rate of the ferry is the same at any time.
The ferry will travel
of the distance in
hours.
If we divide each fraction by 3 ⇒
and

We do this to obtain a ''1'' in the numerator of the second fraction (the hours fraction). Now, we can say that :
The ferry will travel
of the distance in
hours.
Finally, we multiply each fraction by 7 (in order to obtain the distance for 1 hour) ⇒
and

We found out that the ferry will travel
of the distance in 1 hour.