Navigation General · Tides
The total tidal range at a port is 12 feet. Using the Rule of Twelfths, how many feet does the tide rise during the THIRD hour after low water?
- A1 foot
- B2 feet
- C3 feet✓ Correct
- D4 feet
Explanation
Rule of Twelfths: 3rd hour = 3/12 of range. Range = 12 ft. Rise in 3rd hour = (3/12) × 12 = 3 feet. Hours: 1st=1ft, 2nd=2ft, 3rd=3ft, 4th=3ft, 5th=2ft, 6th=1ft (total=12ft).
Authority: Bowditch (Pub. 9), Ch. 9
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