At your current speed of 22 knots you only have enough fuel remaining to travel 422 miles. You must travel 844 miles to reach your destination. What should you reduce your speed (knots) to in order to reach your destination?

Correct Answer: Option A — 15.6

Vessel fuel endurance varies inversely with the cube of the speed. Applying the standard voyage planning proportion $22 \times \sqrt[3]{422 / 844}$ correctly determines the reduced speed of 15.6 knots needed to complete the voyage.