SOLUTION: How many ounces of a 20 % alcohol solution must be mixed with 13 ounces of a 25 % alcohol solution to make a 21 % alcohol​ solution?

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Question 1156588: How many ounces of a 20 % alcohol solution must be mixed with 13 ounces of a 25 % alcohol solution to make a 21 % alcohol​ solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = ounces of 20% alcohol needed
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+%28+.2x+%2B+.25%2A13+%29+%2F+%28+x+%2B+13+%29+=+.21+
+%28+.2x+%2B+3.25+%29+%2F+%28+x+%2B+13+%29+=+.21+
+.2x+%2B+3.25+=+.21%2A%28+x+%2B+13+%29+
+.2x+%2B+3.25+=+.21x+%2B+2.73+
+.01x+=+.52+
+x+=+52+
52 ounces of 20% alcohol are needed
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check:
+%28+.2x+%2B+.25%2A13+%29+%2F+%28+x+%2B+13+%29+=+.21+
+%28+.2%2A52+%2B+.25%2A13+%29+%2F+%28+52+%2B+13+%29+=+.21+
+%28+10.4+%2B+3.25+%29+%2F+65+=+.21+
+10.4+%2B+3.25+=+13.65+
+13.65+=+13.65+
OK