SOLUTION: How much water should be added to 14mL of 9% alcohol solution to reduce the concentration to 7%

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Question 779087: How much water should be added to 14mL of 9% alcohol solution to reduce the concentration to 7%
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +w+ = ml of water to be added
The ml of alcohol never changes
+%28+.09%2A14+%29+%2F+%28+14+%2B+w+%29+=+.07+
+1.26+=+.07%2A%28+14+%2B+w+%29+
+1.26+=+.98+%2B+.07w+
+.07w+=+.28+
+x+=+4+
4 ml of water must be added
check:
+%28+.09%2A14+%29+%2F+%28+14+%2B+w+%29+=+.07+
+%28+.09%2A14+%29+%2F+%28+14+%2B+4+%29+=+.07+
+1.26+=+.07%2A18+
+1.26+=+1.26+
OK