Density=mass/volume. 1) we have to calculate the iron volume in liters. iron volume=second level - first level=49.10 ml-45.50 ml=3.6 ml 3.6 ml=3.6 ml(1 liter / 1000 ml)=0.0036 liters
2) we calculate the mass iron in kg. 28.5 g=28.5 g(1 kg /1000 g)=0.0285 kg. 2) we calculate the density of iron. density=0.0285 kg / 0.0036 liters=7.92 kg/L