Let v1 and v2 be the volumes of the larger and smaller pyramids, and let A1 and A2 be their base areas. v1=A1h1 and v2=A2h2 where h represent the heights. The masses are m1 and m2. We have the following values: h1=12,cm, h2=7.2cm, m1=37.5g. Density=mass/volume, and since the pyramids are similar their density is the same, so d=m1/v1=m2/v2, and m1/m2=v1/v2=A1h1/(A2h2). So 37.5/m2=12A1/(7.2A2). However, the pyramids are geometrically similar. This means that the ratio of the heights of the two pyramids is also the ratio of the sides of their square bases. Thus, if a1 is the base length of the larger pyramid then the base area is a1^2=A1 and A2=a2^2, and h1/h2=a1/a2. The ratio of the areas=A1/A2=a1^2/a^2. But h1/h2=12/7.2=1/0.6=5/3, so A1/A2=(h1/h2)^2=25/9. Therefore, 37.5/m2=12/7.2*25/9=125/27 or (5/3)^3. So m2=37.5*27/125=8.1g.