Bob's Job Shop used one solvent that is 25% acid and a second that is 50% acid. How many liters of each should be mixed to get 10L of a solution that is 40% acid?
let the volume of the 25% solvent be x
then the volume of the 50% solvent is 10-x
.25x + .5(10-x) = .4(10)
times 4
x + 2(10-x) = 16
x + 20 - 2x = 16
-x = -4
x = 4
etc.