Sima is a layer of the Earth's crust that is primarily composed of silicate minerals, such as magnesium and iron silicates. To determine its average density, we can use the formula:
Density = Mass / Volume
We can estimate the mass of a unit volume of sima by looking at the average density of the Earth's crust, which is around 2.7 grams per cubic centimeter. Sima is denser than the average crust, so we can assume a density of around 3.0 grams per cubic centimeter.
Therefore, the answer is 3.0.