SOLUTION: You need 75 mL of a 5% alcohol solution. On hand, you have a 25% alcohol mixture. How much of the 25% alcohol mixture and pure water will you need to obtain the desired solution?

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: You need 75 mL of a 5% alcohol solution. On hand, you have a 25% alcohol mixture. How much of the 25% alcohol mixture and pure water will you need to obtain the desired solution?       Log On

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Question 1054028: You need 75 mL of a 5% alcohol solution. On hand, you have a 25% alcohol mixture. How much of the 25% alcohol mixture and pure water will you need to obtain the desired solution?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = ml of water needed
Let +b+ = ml of 25% alcohol solution needed
+.05%2A75+=+3.75+ ml of alcohol in
your final solution
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(1) +.25b+%2F+%28+a+%2B+b+%29+=+.05+
(2) +.25b+=+3.75+
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(2) +b+=+3.75%2F.25+
(2) +b+=+15+
and
(1) +.25b+=+.05%2A%28+a+%2B+b+%29+
(1) +.25%2A15+=+.05%2A%28+a+%2B+15+%29+
(1) +3.75+=+.05a+%2B+.75+
(1) +.05a+=+3+
(1) +a+=+60+
You need 15 ml of 25% solution
and 60 ml of pure water
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check:
+.25%2A15+%2F+%28+15%2B+60%29+=+.05+
+3.75%2F75+=+.05+
+3.75+=+.05%2A75+
+3.75+=+3.75+
OK