<PRE><B>Question 438100</B>
Here is the question from my book.... Brad is performing an experiment in chemistry class at the University of North Carolina. He needs to mix 20 liters of 40% acid solution with a 70% acid solution to get a mixture that is 50% acid. How many liters of the 70% acid solution should he use
..
let x=liters of 70% solution that should be mixed with 20 liters of the 40% solution
then, x+20 = total amount of liters of final mixtlure
..
40%(20)+70%(x)=50%(x+20)
8+.7x=.5x+10
.2x=2
x=10 liters
ans:

10 liters of 70% solution should be mixed with 20 liters of the 40% solution to get 30 liters that is 50% acid.</PRE>