document.write( "Question 706349: What quantity of 75 per cent acid solution must be mixed with a 25 per cent solution to produce 1080 mL of a 50 per cent solution?
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Algebra.Com's Answer #435100 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = mL of 75% solution needed
\n" ); document.write( "Let $\"+b+\"$ = mL of 25% solution needed
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+a+%2B+b+=+1080+\"$
\n" ); document.write( "(2) $\"+%28+.75a+%2B+.25b+%29+%2F+1080+=+.5+\"$
\n" ); document.write( "------------------------------
\n" ); document.write( "(2) $\"+.75a+%2B+.25b+=+.5%2A1080+\"$
\n" ); document.write( "(2) $\"+.75a+%2B+.25b+=+540+\"$
\n" ); document.write( "(2) $\"+75a+%2B+25b+=+54000+\"$
\n" ); document.write( "Multiply both sides of (1) by $\"+25+\"$
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) $\"+75a+%2B+25b+=+54000+\"$
\n" ); document.write( "(1) $\"+-25a+-+25b+=+-27000+\"$
\n" ); document.write( " $\"+50a+=+27000+\"$
\n" ); document.write( " $\"+a+=+540+\"$
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+540+%2B+b+=+1080+\"$
\n" ); document.write( "(1) $\"+b+=+540+\"$
\n" ); document.write( "540 mL of 75% acid solution must be used
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+%28+.75%2A540+%2B+.25%2A540+%29+%2F+1080+=+.5+\"$
\n" ); document.write( "(2) $\"+%28+405+%2B+135+%29+%2F+1080+=+.5+\"$
\n" ); document.write( "(2) $\"+540+=+.5%2A1080+\"$
\n" ); document.write( "(2) $\"+540+=+540+\"$
\n" ); document.write( "OK
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