How much volume (in cm3) is gained by a person who gains 12.3 lb of pure fat?

So we are given with the mass while we are asked for the amount of volume. So this means, we must need an information on the density. From literature, the density of human fat is 0.918 g/cm³. Convert grams to lb by the conversion that 1,000 g = 2.2 lbs.

Density = 0.918 g/cm³ * (2.2 lbs/1,000 g) = 0.0020196 lb/cm³

Volume = Mass/Density = 12.2 lb / 0.0020196 lb/cm³

Volume = 6,040.8 cm³

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.