The vertex of a great circle track is in LONG 109°E. An eastbound vessel would cross the equator in LONG __________.

Correct Answer: Option D — 161°W

The vertex of a great circle is situated 90° away from the equator. An eastbound vessel passing a vertex at 109°E crosses the equator 90° further along, placing the crossing at 109° + 90° = 199°E, which normalizes to 161°W, per Bowditch.