Answer:
The ratio that doubling length while maintaining shape and density increases volume and mass by 2^3 = 8 works in both directions.
Clearly, from what you wrote, the 1600 pound man 12 feet tall would, if shrunk to half size, would way 1/8 of 1600 pounds, or 200 pounds.
The ratio remains consistent. So a 6 foot tall man weighing 200 pounds, reduced equally in all dimensions with no change in bodily density would be 1/2 of 6 feet tall = 3 feet tall and 1/8 of 200 pounds = 25 pounds.
It is easier to understand this if we use a cube, instead of a person. Picture a cubic volume of ice weighing just one pound. That’’s a cube just about 3 inches on each side. For convenience, let’s call 3 inches one unit.
Please visualize the single cube. The initial cube is 1 unit on each side and weighs one pound.Let’s double its linear dimension, keep it a cube and still ice (same density), and see what we get. Visualize this: a cubic block 2 x 2 x 2 units made of 8 cubic blocks., 2 x 2 x 2 units. Doubling the linear size in 3 dimensions increases volume by 2^3 = 8 times, and increases weight by 8 times, as well.
Explanation: