🔍 Key Concepts

• Parallel sailing uses departure and middle latitude to find distance and course along a parallel • Difference of longitude (DLo) must be converted from degrees and minutes to minutes of arc and then to miles on that latitude • On a parallel of latitude, true course will be either 090°T (east) or 270°T (west) depending on direction of travel

💭 Think About

• Compare the longitudes to decide whether you are sailing east or west and choose between 090°T and 270°T • Compute the difference of longitude in minutes and relate it to the cosine of the latitude to find the departure and distance • Check that the numerical distance you compute is close to one of the options and that the course direction matches the change in longitude

✅ Before You Answer

• Verify which point is further west by comparing the W longitudes; this tells you if you are going toward increasing W or toward decreasing W • Carefully convert degrees and minutes of longitude difference to total minutes before applying the parallel sailing formula • Confirm that your computed distance is within a few miles of one of the choices, and that the associated course (east or west) matches the longitude change