设两种金属质量分别为3m,2m,则
所形成合金体积为(3m/p1)+(2m/p2)=(3m*p2+2m*p1)/(p1*p2)
所以密度为(3m+2m)/[(3m*p2+2m*p1)/(p1*p2)]=5p1p2/(3p2+2p1)