Question

两个杯子中分别装有浓度为40%与10%的食盐水,倒在一起混合后,食盐水的浓度为30%,若再加入300克20%的水,

Answer 1

设40%的有X克,10%的有Y克,(40%X+10%Y)/(X+Y)=30%,

(40%X+10%Y+300*20%)/(300+X+Y)=25%