Answer:
The density of the material must be at least 1.5 g/cm³.
Explanation:
The volume for a pyramid is given by the following formula:
V = (1/3)*Abase*h
Where V is the volume, Abase is the base area and h is the height. For Alexis's pyramid, we have:
V = (1/3)*100*6 = 200 cm³
Since he wants the paperweigth to have a mass of at least 300 grams, the density must be at least:
density = mass/volume = 300/200 = 1.5 g/cm³