Question

One solution contains 50% alcohol and another solution contains 80% alcohol. How many liters of each solution should be mixed to produce 10.5 liters of a 70% alcohol situation?

Answer 1

x(.5) + y(.8) = 10.5(.7)

x+y=10.5
x=(10.5-y)

(10.5 -y)(.5) + .8y = 7.35
5.25 -.5y +.8y = 7.35
.3y = 7.35 - 5.25
.3y = 2.1
y= (2.1)/(.3) = 21/3 = 7

x+7 = 10.5
x= 3.5

Double check:

3.5(.5) + 7(.8) = 10.5(.7)
1.75 + 5.6 = 7.35
7.35 = 7.35 (GOOD)

x= 3.5(50%); and y=7(80%)