Chart Navigation & Plotting · Distance, Speed & Time
Using the three-minute rule, a vessel that travels 600 yards in 3 minutes is making approximately:
- A3 knots
- B6 knots✓ Correct
- C10 knots
- D12 knots
Explanation
By the three-minute rule, speed in knots equals yards traveled in 3 minutes divided by 100. 600 ÷ 100 = 6 knots. It is a quick mental check handy in pilotage waters.
Authority: Bowditch, Pub. No. 9 (three-minute rule)
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