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Before assigning this activity, you might explain that a nautical mile is the distance of one minute, or 1/60th of a degree, of the equator’s 360-degree circumference.

Can You Fathom This?
Measuring Nautical Speed and Ocean Depth

Ships record their speed in knots. One knot is the speed of one nautical mile per hour. A nautical mile is 6,076 feet. On land a mile is 5,280 feet. Ocean depth is measured in fathoms, with one fathom equaling six feet. Use this information to solve the problems below.

 1. How much longer is a nautical mile than a land mile? 796 feet longer 2. A ship traveling 10 knots is traveling at what speed in land miles per hour? 11.5 miles per hour 3. A sunken ship buried at a depth of 48 fathoms is how many feet below the surface of the water? 288 feet 4. (a) Some whales are said to dive half a mile below the surface. If the statement is referring to land miles, how many fathoms is this? 440 fathoms (b) If this statement is referring to nautical miles, how many fathoms is this? 506 1/3 fathoms Extra Credit: How did the term knot become used as a measure of speed? From counting the number of knots that ran out in the line tied to the chip log used to measure speed.

Have on Hand- photocopies of blank worksheet

Blank Worksheet (pdf)