Answer:
8.29 g/cm³
Step-by-step explanation:
Average density = total mass / total volume
volume of Cu present = 63.5 wt% / 8.94 g/cm3 = 7.1029 cm³
volume of Zn = 33.5 wt% / 7.13 g/cm3 = 4.6985 cm³
volume of Pb = 3.0 wt% / 11.35 g/cm3 = 0.26432 cm³
average density = 100 g / (7.1029 cm³+4.6985 cm³+0.26432 cm³) = 8.29 g/cm³