document.write( "Question 209326: Please help me with the following word problem, I can not do percentages at all and I can not figure out the answer. Thank you so much! A chemist wants to mix a 5% alcohol solution with a 25% alcohol solution to obtain 8 liters of a 20% alcohol solution. How much (in liters) of the 25% solution should she use? \n" ); document.write( "
Algebra.Com's Answer #158244 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
What might help you is to always
\n" ); document.write( "remember that percent means
\n" ); document.write( "\"per one-hundred\", so whenever
\n" ); document.write( "you see %, you must divide by
\n" ); document.write( "100.
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\n" ); document.write( "A good question to ask with this
\n" ); document.write( "problem is: \"How much water and
\n" ); document.write( "how much alcohol end up in the
\n" ); document.write( "final solution?
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\n" ); document.write( "Let \"a\"= liters of the 5% solution added
\n" ); document.write( "Let \"b\"= liters of the 25% solution added
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\n" ); document.write( "The equation to solve in words is:
\n" ); document.write( "(alcohol in 5% solution)+(alcohol in 25% soltion)/(alcohol + water in 20% solution) = 20%
\n" ); document.write( "So, I can write:
\n" ); document.write( "(1) \"%28.05a+%2B+.25b%29+%2F+8+=+.2\"
\n" ); document.write( "(2) \"a+%2B+b+=+8\"
\n" ); document.write( "Multiply both sides of (1) by \"8\"
\n" ); document.write( "(1) \".05a+%2B+.25b++=+8%2A.2\"
\n" ); document.write( "(1) \".05a+%2B+.25b+=+1.6\"
\n" ); document.write( "Multiply both sides of (2) by \".05\" and subtract from (1)
\n" ); document.write( "(2) \".05a+%2B+.05b+=+.05%2A8\"
\n" ); document.write( "(2) \".05a+%2B+.05b+=+.4\"
\n" ); document.write( "And, subtracting:
\n" ); document.write( "(1) \".05a+%2B+.25b+=+1.6\"
\n" ); document.write( "(2) \"-.05a+-+.05b+=+-.4\"
\n" ); document.write( "\".2b+=+1.2\"
\n" ); document.write( "\"b+=+6\"
\n" ); document.write( "She should use 6 liters of the 25% solution
\n" ); document.write( "check answer:
\n" ); document.write( "(2) \"a+%2B+b+=+8\"
\n" ); document.write( "\"a+%2B+6+=+8\"
\n" ); document.write( "\"a+=+2\"
\n" ); document.write( "Go back to (1)
\n" ); document.write( "(1) \"%28.05a+%2B+.25b%29+%2F+8+=+.2\"
\n" ); document.write( "\"%28.05%2A2+%2B+.25%2A6%29+%2F+8+=+.2\"
\n" ); document.write( "\".05%2A2+%2B+.25%2A6+=+1.6\"
\n" ); document.write( "\".1+%2B+1.5+=+1.6\"
\n" ); document.write( "\"1.6+=+1.6\"
\n" ); document.write( "It always helps if you can sum up the problem in
\n" ); document.write( "an equation with words like I did (It helps me a lot)\r
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