document.write( "Question 411740: how many gallons of 90% antifreeze solution must be mixed with 90 gallons of 30% antifreeze to get a mixture that is 80% antifreeze \n" ); document.write( "

Algebra.Com's Answer #289341 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"a\"$ = gallons of 90% antifreeze needed
\n" ); document.write( " $\"%28.9a+%2B+.3%2A90%29+%2F+%28a+%2B+90%29+=+.8\"$
\n" ); document.write( " $\"%28.9a+%2B+27%29+%2F+%28a+%2B+90%29+=+.8\"$
\n" ); document.write( " $\".9a+%2B+27+=+.8%2A%28a+%2B+90%29\"$
\n" ); document.write( " $\".9a+%2B+27+=+.8a+%2B+72\"$
\n" ); document.write( " $\".1a+=+45\"$
\n" ); document.write( " $\"a+=+450\"$
\n" ); document.write( "450 gallons of 90% antifreeze are needed
\n" ); document.write( "check:
\n" ); document.write( " $\"%28.9a+%2B+.3%2A90%29+%2F+%28a+%2B+90%29+=+.8\"$
\n" ); document.write( " $\"%28.9%2A450+%2B+.3%2A90%29+%2F+%28450+%2B+90%29+=+.8\"$
\n" ); document.write( " $\"%28405+%2B+27%29+%2F+540+=+.8\"$
\n" ); document.write( " $\"432%2F540+=+.8\"$
\n" ); document.write( " $\"432+=+.8%2A540\"$
\n" ); document.write( " $\"432+=+432\"$
\n" ); document.write( "OK \n" ); document.write( "

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