🔍 Key Concepts

• Parallel sailing uses difference of longitude and the cosine of latitude to find distance and departure • Convert longitudes correctly when crossing the 180° meridian (International Date Line) • On a parallel of latitude, the true course is either due east (090° T) or due west (270° T)

💭 Think About

• First decide whether you are going east or west: compare the initial W longitude with the final E longitude, keeping in mind the 180° meridian • Compute the smaller arc of longitude between the two meridians by working through 169° 38' W → 180° → 174° 52' E • Use the parallel sailing relation: Distance on that parallel = (Difference of longitude in minutes) × cos(latitude); then compare with the answer options

✅ Before You Answer

• Confirm whether the vessel must steer 090° T or 270° T along the parallel at 16° 24' S • Carefully calculate the total difference of longitude in degrees and minutes when crossing 180° • Convert the difference of longitude to nautical miles at that latitude using the cosine of latitude before matching to the closest distance option