SOLUTION: Roberto needs a solution that is 30% silver nitrate. He has 12 ounces of a 25% silver nitrate solution. How many ounces of a 40% silver nitrate solution should he add to make a sol

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Question 940543: Roberto needs a solution that is 30% silver nitrate. He has 12 ounces of a 25% silver nitrate solution. How many ounces of a 40% silver nitrate solution should he add to make a solution that is 30% silver nitrate?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = ounces of 40% solution to be added
+.4x+ = ounces of silver nitrate in 40% solution
+.25%2A12+=+3+ = ounces of silver nitrate in 25% silver nitrate solution
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+%28+3+%2B+.4x+%29+%2F+%28+12+%2B+x+%29+=+.3+
+3+%2B+.4x+=+.3%2A%28+12+%2B+x+%29+
+3+%2B+.4x+=+3.6+%2B+.3x+
+.1x+=+.6+
+x+=+6+
6 ounces of the 40% solution should be added
check:
+%28+3+%2B+.4x+%29+%2F+%28+12+%2B+x+%29+=+.3+
+%28+3+%2B+.4%2A6+%29+%2F+%28+12+%2B+6+%29+=+.3+
+5.4+%2F+18+=+.3+
+5.4+=+5.4+
OK