现有含盐7%的盐水21千克,要把盐水的浓度增加到10%,有几种方法?

1加盐x(kg)(x+21*7%)/(x+21)*100%=10%x+1.47=(x+21)*10%x+1.47=0.1x+2.10.9x=0.63x=0.72蒸馏水x(kg)(21*7%)/(21-x)*100%=10%1.47=(21-x)*10%1.47=2.1-0.1x0.1x=0.63x=6.3