Chart Navigation & Plotting · Speed-Time-Distance
A vessel makes good 18 nautical miles in 1 hour 12 minutes. What is her speed over the ground?
- A12.0 knots
- B15.0 knots✓ Correct
- C16.2 knots
- D21.6 knots
Explanation
Speed = distance / time. 1 h 12 m = 1.2 h. 18 / 1.2 = 15.0 knots. The classic 60·D = S·T relationship (60 × 18 = S × 72 → S = 15) gives the same answer.
Authority: Bowditch, American Practical Navigator (Pub. 9)
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