ρ=m/V V=m/ρ
m金+m铜=20g
V金+V铜=m金/ρ金+m铜/ρ铜=1.8cm³
(20g-m铜)/19.3g/³ +m铜/8.9g/cm³=1.8cm³
得到 m铜=12.61g
m金=20g-12.61g=7.39g