SOLUTION: A nurse has 1 liter of a solution that is 10% alcohol. How much pure alcohol must she add to bring it to a solution that contains 25% alcohol? (Hint: A pure alcohol solution contai

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Question 661367: A nurse has 1 liter of a solution that is 10% alcohol. How much pure alcohol must she add to bring it to a solution that contains 25% alcohol? (Hint: A pure alcohol solution contains 100% alcohol)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = liters of pure alcohol she must add
+.1%2A1+=+.1+ = liters of alcohol in 10% solution
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+%28+.1+%2B+x+%29+%2F+%28+1+%2B+x+%29+=+.25+
+.1+%2B+x+=+.25%2A%28+1+%2B+x+%29+
+.1+%2B+x+=+.25+%2B+.25x+
+.75x+=+.15+
+x+=+.15%2F.75+
+x+=+.2+
She must add .2 liters of pure alcohol
check:
+%28+.1+%2B+x+%29+%2F+%28+1+%2B+x+%29+=+.25+
+%28+.1+%2B+.2+%29+%2F+%28+1+%2B+.2+%29+=+.25+
+.3+%2F+1.2+=+.25+
+.3+=+.25%2A1.2+
+.3+=+.3+
OK