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 C — 176°36'E

For an easterly or westerly course along a parallel of latitude, difference of longitude is calculated using $\text{DLo} = \frac{\text{Departure}}{\cos(\text{Lat})}$. Steaming 179 miles due west (270°) from 178°35.0'W at LAT 51°48'S changes longitude by 288.6 minutes, resulting in 176°36'E.