SOLUTION: 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

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Question 438100: 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?
I think the answer is 15 but when i tried to work it out I got confused. this is what I have so far: 20/15 = 1.333333333, 1.333333333/70= 50, 1.333333333 X 70 = 50, well anyways you see I didn't get to far.
thank you.
Found 3 solutions by scott8148, lwsshak3, ankor@dixie-net.com:
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
(20)(40%) + (x)(70%) = (20 + x)(50%)

Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
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.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
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 = amt of 70% solution required
:
Write an amt of acid equation in decimal form:
.40(20) + .70x = .50(x+20)
:
8 + .70x = .50x + 10
:
.70x - .50x = 10 - 8
:
.20x = 2
x = 2%2F.2
x = 10 liters of 70% solution
:
:
Confirm the solution
.4(20) + .7(10) = .5(10+20)
8 + 7 = .5(30)