设原溶液的质量为m1,加水后溶液的质量为m2
m1×30%=m2×24%
m2=1.25m1
m水=m2-m1=1.25m1-m1=0.25m1
则现加入等量的水后酒精的质量分数为:
(30%m1)/(m1+0.25m1+0.25m1)×100%=20%
设原溶液的质量为m1,加水后溶液的质量为m2
m1×30%=m2×24%
m2=1.25m1
m水=m2-m1=1.25m1-m1=0.25m1
则现加入等量的水后酒精的质量分数为:
(30%m1)/(m1+0.25m1+0.25m1)×100%=20%