SOLUTION: How many liters of pure alcohol must be added to 7 liters of a 84% solution of alcohol to make a 93% solution?

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Question 1006734: How many liters of pure alcohol must be added to 7 liters of a 84% solution of alcohol to make a 93% solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = liters of pure alcohol to be added
+.84%2A7+=+5.88+ liters of alcohol in 84% solution
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+%28+x+%2B+5.88+%29%2F+%28+x+%2B+7+%29+=+.93+
+x+%2B+5.88+=+.93%2A%28+x+%2B+7+%29+
+x+%2B+5.88+=+.93x+%2B+6.51+
+.07x+=+.63+
+x+=+9+
9 liters of alcohol must be added
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check:
+%28+x+%2B+5.88+%29%2F+%28+x+%2B+7+%29+=+.93+
+%28+9+%2B+5.88+%29%2F+%28+9+%2B+7+%29+=+.93+
+14.88+%2F+16+=+.93+
+14.88+=+14.88+
OK