Rule of twelfths use

• A. Estimate tide height at mean sea level
• B. Predict wind direction
• C. Determine current speed
• D. Estimate tide height between highs and lows

Answer: (D)

The main idea tested is using the rule of twelfths to estimate how high the tide is at a given time between low and high tide. This rule splits the rise (or fall) into approximate chunks: about 1/12 of the total range in the first hour after low tide, about 2/12 in the second hour, about 3/12 in the third hour, and about 6/12 in the fourth hour. The same pattern applies in reverse when the tide is falling. With this quick mental model, you can estimate water depth at intermediate times without a chart.

So this tool is used to estimate tide height between highs and lows, which is especially helpful for judging depth when paddling across shallow bars or through narrow channels. It isn’t about predicting wind direction, current speed, or the tide height at mean sea level, and it’s a rough estimate intended for planning rather than precise measurements.