document.write( "Question 691502: How many mL of a 20% acid should Paul mix with a 60% acid solution to make 100 mL of 50% acid solution? \n" ); document.write( "

Algebra.Com's Answer #426738 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = ml of 20% solution needed
\n" ); document.write( "Let $\"+b+\"$ = ml of 60% solution needed
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+a+%2B+b+=+100+\"$
\n" ); document.write( "(2) $\"+%28+.2a+%2B+.6b+%29+%2F+100+=+.5+\"$
\n" ); document.write( "---------------------------
\n" ); document.write( "(2) $\"+.2a+%2B+.6b+=+50+\"$
\n" ); document.write( "(2) $\"+2a+%2B+6b+=+500+\"$
\n" ); document.write( "Multiply both sides of (1) by $\"+2+\"$
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) $\"+2a+%2B+6b+=+500+\"$
\n" ); document.write( "(1) $\"+-2a++-+2b+=+-200+\"$
\n" ); document.write( " $\"+4b+=+300+\"$
\n" ); document.write( " $\"+b+=+75+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+a+%2B+b+=+100+\"$
\n" ); document.write( "(1) $\"+a+%2B+75+=+100+\"$
\n" ); document.write( "(1) $\"+a+=+25+\"$
\n" ); document.write( "25 ml of 20% solution is needed
\n" ); document.write( "75 ml of 60% solution is needed
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+%28+.2a+%2B+.6b+%29+%2F+100+=+.5+\"$
\n" ); document.write( "(2) $\"+%28+.2%2A25+%2B+.6%2A75+%29+%2F+100+=+.5+\"$
\n" ); document.write( "You can finish the check
\n" ); document.write( " \n" ); document.write( "

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