Question 500261
How much water must be evaporated from the 15 liters of the 12 percent dye solution to obtain a solution that is 20 percent dye? 
Assume that the total amount of dye is not affected by the process of evaporation.
:
Let x = amt that has to be evaporated to accomplish this
:
.12(15) = .20(15 - x)
1.8 = 3 - .2x
.2x = 3 - 1.8
.2x = 1.2
x = {{{1.2/.2}}} 
x = 6 liters has to be evaporated
:
:
We can confirm this, the amt of dye remains the same (only the percent changes)
.12(15) = .20(15 - 6)
1.8 = .20(9)
1.8 = 1.8 liters is the amt of dye