document.write( "Question 865059: You need a 15% solution. You are going to mix 10 liters of a 27% solution with an amount of a 10% solution. How much of the 10% solution should you use? \n" ); document.write( "
Algebra.Com's Answer #521480 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let's say this solution is a mixture of water and alcohol. \r
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\n" ); document.write( "\n" ); document.write( "We have \"10 liters of a 27% solution\", so we have 10*0.27 = 2.7 liters of pure alcohol. \r
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\n" ); document.write( "\n" ); document.write( "Let x be the amount of the 10% solution we have. This amount will be in liters. So for this portion, we have 0.10x liters of pure alcohol.\r
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\n" ); document.write( "\n" ); document.write( "Combine the two pure amounts: 2.7 + 0.10x
\n" ); document.write( "That's as far as you can go for that bit. We have a total of 2.7 + 0.10x liters of pure alcohol.\r
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\n" ); document.write( "\n" ); document.write( "This is out of a total of 10+x liters of solution (10 from the first bit, x from the second)\r
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\n" ); document.write( "\n" ); document.write( "This ratio is \"%282.7+%2B+0.10x%29%2F%2810%2Bx%29\" and this represents the fraction of pure alcohol over the total amount of solution. We want this fraction to be equal to 0.15 (15%) since we want a 15% solution at the end. So set it equal to 0.15 and solve for x\r
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\n" ); document.write( "\n" ); document.write( "\"%282.7+%2B+0.10x%29%2F%2810%2Bx%29=0.15\"\r
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\n" ); document.write( "\n" ); document.write( "\"2.7+%2B+0.10x=0.15%2810%2Bx%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"2.7+%2B+0.10x=0.15%2810%29%2B0.15%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"2.7+%2B+0.10x=1.5%2B0.15x\"\r
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\n" ); document.write( "\n" ); document.write( "\"2.7+%2B+0.10x-0.15x=1.5\"\r
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\n" ); document.write( "\n" ); document.write( "\"0.10x-0.15x=1.5-2.7\"\r
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\n" ); document.write( "\n" ); document.write( "\"-0.05x=-1.2\"\r
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\n" ); document.write( "\n" ); document.write( "\"x=-1.2%2F%28-0.05%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x=24\"\r
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\n" ); document.write( "\n" ); document.write( "Remember that we made x equal to the amount of 10% solution we'll mix in. So because the initial problem is asking for that, we can stop here.\r
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\n" ); document.write( "\n" ); document.write( "So we must mix in 24 liters of the 10% alcohol solution with 10 liters of the 27% alcohol solution to get a final solution of 15% alcohol.\r
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\n" ); document.write( "\n" ); document.write( "Final Answer: 24 liters
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