A piece of wood was thrown from the ship into the sea, with a thin rope attached to it. As the ship sailed on, the wood remained bobbing in the water at about the same place; the rope unwound as the ship sailed by and away from the wood. By leaving the wood, or “log” as English sailors called it, in the water for a minute . . . the seaman would know how far the ship had traveled in that time, and so work out how far it had traveled in an hour. . . . [i]f a knot were tied in the rope every one-sixtieth of a mile, all a sailor had to do was to count the knots as he pulled in the rope, and he would know how many miles per hour his ship was traveling.”

How did tying knots in the rope make the job of figuring out how far a ship had traveled easier

do not make me regert typing all of this

Explanation:

Interesting text. Reading it, I have learned where the measure knots, used for the speed of boats, come from!

Tying knots in the rope made the job of figuring out how far a ship had traveled easier because the knots were uniformly spaced along the rope, as it is said 1/16 of a mile. Then, when a specific time elapsed, the rope was pulled in and the number of knots on the rope were counted.

Then, the speed would be the number of knots divided by the time.

If the time was one hour, then the number of knots were directly the speed on an hour basis. If the time was, different, say 15 mimutes, you just need to multiply by 4 (thera are 4 times 15 minutes in an hour) to have the number of knots in an hour. Standardizing the time to an hour tells directamente the speed in number of knots.

Suppose that the sailor counted 200 knots,  in an hour, the the speed was 200 knots which is equivalent to 200 × 1/16 miles per hour = 12.5 miles per hour.