486. Your vessel receives a distress call from a vessel reporting her position as LAT 35°01'S, LONG 18°51'W. Your position is LAT 30°18'S, LONG 21°42'W. Determine the true course from your vessel to the vessel in distress by Mercator sailing.

The correct course is 153 true. This was determined by calculating the difference in latitude and longitude, finding the departure using the mean latitude, and then applying the formula tan C = Dep/DLat to find the angle east of south. This angle was then converted to a true course by subtracting it from 180.