The liquid mud tanks on your vessel measure 24'L by 16'B by 8'D. The vessel's displacement in salt water (specific gravity 1.025) is 864 T and the specific gravity of the mud is 1.47. What is the reduction in GM due to 2 of these tanks being slack?

Correct Answer: Option B — 0.78 foot

Free surface reduction of GM is independent of the vessel's water density and depends only on tank geometry, fluid specific gravity, and ship displacement. Using the formula for two 24'x16' tanks with 1.47 SG mud at 864 T displacement yields a 0.78-foot reduction.