Conchita has two solutions available in the lab, one with 10% alcohol and another with 20% alcohol. How much of each should she mix together to make 30 ml of a 14% alcohol solution?

Answer 1

.10(30-x) + .20(x) = .14(30)

3-.1x +.2x = 4.2

.1x = 4.2-3 = 1.2

x=1.2/.1 = 12 mil of 20%

30-x =30-12 = 18 ml of 10%

to form a mixture or 30 ml of 14%

.2(12) + .1(18) = 2.4 + 1.8 = 4.2

.2 is within .06 of .14,

.1 is within .04 of .14

you need more of the solution that's closer to 14%

.04/.06 = 2/3 = 12/18