瓶的容积不变,水和另-液体的体积V相等
V=m/p=M水/p水=M液/p液
(0.4-0.1)/p水=(0.64-0.1)/p液
p液=[(0.64-0.1)/(0.4-0.1)]*p水
=1.8*10^3kg/m^3