You are turning 78 RPM, with a propeller pitch of 21 feet, and an estimated slip of - 7%. What is the speed of advance?

Correct Answer: Option C — 17.3 knots

Calculating vessel speed with propeller RPM of 78, pitch of 21 feet, and a negative slip of -7% involves multiplying revolutions by pitch per minute, converting to nautical miles, and adjusting for negative slip to yield 17.3 knots.