Chart Navigation & Plotting · Tides — Rule of Twelfths
With a 9-foot range (6-hour rise), how much has the tide risen 1 hour after low water?
- A0.75 feet✓ Correct
- B1.5 feet
- C3.0 feet
- D0.9 feet
Explanation
In the first hour the tide rises 1/12 of the range: (1/12) × 9 ft = 0.75 ft.
Authority: Bowditch (Pub. No. 9); NOAA Tide Tables
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