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Solution

Calatima A200 weighs 3.6kg when full, and it looses 2.2kg when submerged. It carries 90l of breathing gas, which is 0.9kg. This means, that when you have depleted the tank, it will weigh: 3.6 – 2.2 – 0.9 = 0.5kg underwater.

Using similar logic, you will get the following values for the other two tanks:

  • Luxfer TM26: 8.1 – 6.2 – 4.4 = -2.5 (it wants to float!)
  • Luxfer HY34: 14.9 – 8.3 – 11.1 = -4.5 (it wants to float!)

So once you are at the deepest point of the dive (all 3 tanks are empty) you will require 0.5 + (-2.5) + (-4.5) = 6.5kg extra weight to avoid floating.

Since the ship has only 1kg weights, you will have to round this value up. As such, the solution is: 7

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