You depart LAT 51°48.0'S, LONG 178°35.0'W and steam 179 miles on course 270°. What is the longitude of arrival?

Correct Answer: Option A — 176°36'E

In parallel sailing, departure equals change in longitude times the cosine of the latitude. Since the course is 270° (due west), the change in longitude is calculated by dividing the departure (179 miles) by the cosine of 51°48'S. This results in a longitude change of 289.5', moving the vessel to 176°36'E.