SOLUTION: A chemist must mix 8 liters of 40% acid solution with some 70% solution to obtain a 50% solution. How much of the 70% solution should be used?

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Question 183925: A chemist must mix 8 liters of 40% acid solution with some 70% solution to obtain a 50% solution. How much of the 70% solution should be used?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
.70x+.40*8=.50(8+x)
.70x+3.2=4+.50x
.70x-.50x=4-3.2
.20x=.8
x=.8/.2
x=4 liters of 70% acid is used.
Proof:
.70*4+.4*8=.5(8+4)
2.8+3.2=.5*12
6=6