Answer:
2.9g/cm^3
Explanation:
We're given that the mass of the system before the rock was added was
120g . The mass after the rock was added was 250g, so the rock's mass is 130g.
The initial volume of water in the graduated cylinder was
30 mL , and the volume after the rock was added read 75mL , so the rock's volume is 45mL
Density = Mass over Volume.
AKA. 130g/45mL
2.9g/cm^3 (rounded)