SOLUTION: How much pure alcohol must a nurse add to 10 cm^3 of a 60% alcohol solution to strengthen it to a 90% solution?

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Question 947477: How much pure alcohol must a nurse add to 10 cm^3 of a 60% alcohol solution to strengthen it to a 90% solution?
Found 2 solutions by Alan3354, josmiceli:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
How much pure alcohol must a nurse add to 10 cm^3 of a 60% alcohol solution to strengthen it to a 90% solution?
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Add x cc
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10*60 + x*100 = (10+x)90

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = cm3 of pure alcohol to be added
+.6%2A10+=+6+ cm3 of pure alcohol in 60% solution
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+%28+x+%2B+6+%29+%2F+%28+x+%2B+10+%29+=+.9+
+x+%2B+6+=+.9%2A%28+x+%2B+10+%29+
+x+%2B+6+=+.9x+%2B+9+
+.1x+=+3+
+x+=+30+
30 cm3 of pure alcohol should be added
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check:
+%28+x+%2B+6+%29+%2F+%28+x+%2B+10+%29+=+.9+
+%28+30+%2B+6+%29+%2F+%28+30+%2B+10+%29+=+.9+
+36+%2F+40+=+.9+
+36+=+.9%2A40+
+36+=+36+
OK