数学题说出为啥?

问题描述:

数学题说出为啥?
Juan made 2L of lemonade that consists of 40% pure lemon juice.How much water must he add to dilute it to 30%lemon juice
A:1/3 liter
B:1/2 liter
C:2/3 liter
D:1/1/3 liters
公式为2(0.4)= X(0.3)
求出X
并选出是几

你设的x是总体积 =8/3
要减去原体积8/3-2=2/3
或设加水为x
则2*0.4=(x+2)*0.3
x=2/3
选C