In order to calculate the TPI of a vessel, for any given draft, it is necessary to divide the area of the waterplane by __________.
Official USCG Answer & Rule Citation
Correct Answer: Option D — 420
Tons per Inch immersion (TPI) is derived by dividing the waterplane area in square feet by 420, reflecting the density factor of saltwater at 35 cubic feet per long ton multiplied by 12 inches per foot.
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