A chemist has a solution that is 70% acid and another that is 45% acid. How many liters of each should he mix to obtain 300 liters of a solution that is 65% acid?

Answer 1

amount of the 70% solution --- x L
amount of the 45% solution--- 300-x L

.70x + .45(300-x) = .65(300)
time 100
70x + 45(300-x) = 65(300
70x + 13500 - 45x = 19500
25x = 6000
x = 240

So 240 L of the 70% stuff, and 60 L of the 45% stuff

check:
.7(240) + .45(60) = 195
.65(300) = 195
looks good to me