On a vessel of 5,000 tons displacement there are two slack tanks of acid (SG 1.8). Each tank is 30 feet long and 20 feet wide. What is the reduction in metacentric height due to free surface with the vessel in sea water (SG 1.025)?

Correct Answer: Option C — .40 ft

Acid with a high specific gravity of 1.8 significantly magnifies free surface effects. Computing two 30'x20' slack tanks on a 5,000-ton vessel in saltwater gives a total metacentric height reduction of 0.40 feet.