Answer: 1500kg/m^3
Explanation: Assuming the cube was not large enough to float if it displaced 30cm^3 of water then it has a volume of 30cm^3. Density is just mass/volume so 45g/30cm^3 = 1.5g/cm^3. To convert this to kg/m we need to multiply by the conversion factors of the units. 1.5g/cm^3 • 1kg/1000g • 1,000,000cm^3/1m^3 = 1500kg/m^3.
