You are underway on course 215°T at 12 knots. The current is 000°T at 2.3 knots. What is the speed being made good?

Correct Answer: Option B — 10.2 knots

The current is setting at 000° while the vessel is on course 215°. The angle between the course and current is 145°. Using the law of cosines to find the resultant vector, the speed made good is reduced to 10.2 knots, accounting for the opposing component of the current.