document.write( "Question 533274: You are making 10 tons of concrete that is 48.5% cement by mixing a 12% cement mixture with a 85% cement mixture. How much of the 85% cement mixture must you use? How much of the 12% cement mixture must
\n" ); document.write( "you use \n" ); document.write( "

Algebra.Com's Answer #351027 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = tons of 12% mixture needed
\n" ); document.write( "Let $\"+b+\"$ = tons of 85% mixture needed
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+a+%2B+b+=+10+\"$
\n" ); document.write( "(2) $\"+%28+.12a+%2B+.85b+%29+%2F+10+=+.485+\"$
\n" ); document.write( "----------------------------
\n" ); document.write( "(2) $\"+.12a+%2B+.85b+=+10%2A.485+\"$
\n" ); document.write( "(2) $\"+.12a+%2B+.85b+=+4.85+\"$
\n" ); document.write( "(2) $\"+12a+%2B+85b+=+485+\"$
\n" ); document.write( "Multiply both sides of (1) by $\"+12+\"$
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) $\"+12a+%2B+85b+=+485+\"$
\n" ); document.write( "(1) $\"+-12a+-+12b+=+-120+\"$
\n" ); document.write( " $\"+73b+=+365+\"$
\n" ); document.write( " $\"+b+=+5+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+a+%2B+b+=+10+\"$
\n" ); document.write( "(1) $\"+a+=+10+-+5+\"$
\n" ); document.write( "(1) $\"+a+=+5+\"$
\n" ); document.write( "5 tons of 12% mixture are needed
\n" ); document.write( "5 tons of 85% mixture are needed
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+%28+.12%2A5+%2B+.85%2A5+%29+%2F+10+=+.485+\"$
\n" ); document.write( "(2) $\"+%28+.6+%2B+4.25+%29+%2F+10+=+.485+\"$
\n" ); document.write( "(2) $\"+4.85+%2F+10+=+.485+\"$
\n" ); document.write( "(2) $\"+4.85+=+4.85+\"$
\n" ); document.write( "OK \n" ); document.write( "

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