甲的密度:ρ甲 = m甲 / V甲 = 2.7 kg / 1 dm3 = 2.7 kg/dm3 (= 2.7 g/cm3)
乙的密度:ρ乙 = m乙 / V乙 = 2.7 kg / 3 dm3 = 0.9 kg/dm3 (= 0.9 g/cm3)