试题分析:
解:甲的体积:V甲=0.1m×0.1m×0.1m=0.001m3,则甲的密度:ρ甲= m甲 /V甲 = 3kg /0.001m3 =3×103kg/m3;
乙的体积:V乙=0.2m×0.2m×0.2m=0.008m3,则乙的密度:ρ乙= m乙 /V乙 = 21.6kg /0.008m3 =2.7×103kg/m3;
丙的体积:V丙=0.3m×0.3m×0.3m=0.027m3,则丙的密度:ρ丙= m丙 /V丙 = 54kg /0.027m3 =2×103kg/m3.
因为ρ乙=ρ铝,所以乙是合格品;因为ρ丙<ρ铝,所以丙是废品;因为ρ甲>ρ铝,所以甲是次品.
故选 :C
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