The question refers to a table of hydrostatic data from which the TPC at a draught of 5.05 m is to be calculated. The table is not reproduced here, but the standard method is as follows.

Method:

• The TPC (tonnes per centimetre immersion) is the change in displacement (in tonnes) for a 1 cm change in draught.
• TPC = (waterplane area x density of sea water)/100, where the waterplane area is in m2 and the density is 1.025 tonne/m3 for sea water.
• Alternatively, TPC = (change in displacement)/(change in draught in cm) between two adjacent draughts in the hydrostatic table.
• To find the TPC at 5.05 m, take the waterplane area at the draught of 5.05 m from the hydrostatic curves (or interpolate between the waterplane areas at the draughts immediately above and below 5.05 m), and apply the formula.

Working example (assuming the table gives waterplane area at draughts):

• If the waterplane area at 5.05 m is A m2, then TPC = (A x 1.025)/100 tonne/cm.
• If the table gives displacement at successive draughts, then TPC at 5.05 m = (displacement at 5.10 m - displacement at 5.00 m)/10, i.e. the change in displacement for a 10 cm change divided by 10.

Since the specific table values are not available in this question paper, the candidate should read the waterplane area (or the displacement change) at 5.05 m from the given hydrostatic data and apply the formula above to obtain the TPC. The answer will be the TPC in tonne/cm at a draught of 5.05 m.