document.write( "Question 783163: a tank holds 80 liters of a chemical solution. Currently, the solution has a strength of 30%. how much of this should be drained, and replaced with a 70% solution, to get a final strength of 40%? \n" ); document.write( "

Algebra.Com's Answer #476639 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+x+\"$ = liters to be drained
\n" ); document.write( " $\"+.3x+\"$ = liters of chemical in $\"+x+\"$ liters of solution
\n" ); document.write( "-----------------------------------------------
\n" ); document.write( " $\"+x+\"$ liters of 30% solution are replaced with $\"+x+\"$
\n" ); document.write( "liters of 70% solution
\n" ); document.write( " $\"+.7x+\"$ = liters of chemical in 70% solution
\n" ); document.write( "Note that total liters of solution doesn't change
\n" ); document.write( "--------------------------------------
\n" ); document.write( " $\"+.3%2A80+=+24+\"$ liters of chemical in $\"+80+\"$ liters of solution
\n" ); document.write( " $\"+%28+24+-+.3x+%2B+.7x+%29+%2F+80+=+.4+\"$
\n" ); document.write( " $\"+%28+24+%2B+.4x+%29+%2F+80+=+.4+\"$
\n" ); document.write( " $\"+24+%2B+.4x+=+32+\"$
\n" ); document.write( " $\"+.4x+=+8+\"$
\n" ); document.write( " $\"+x+=+20+\"$
\n" ); document.write( "20 liters should be drained & replaced with 70% solution
\n" ); document.write( "check:
\n" ); document.write( " $\"+%28+24+-+.3x+%2B+.7x+%29+%2F+80+=+.4+\"$
\n" ); document.write( " $\"+%28+24+-+.3%2A20+%2B+.7%2A20+%29+%2F+80+=+.4+\"$
\n" ); document.write( " $\"+%28+24+-+6+%2B+14+%29+%2F+80+=+.4+\"$
\n" ); document.write( " $\"+32%2F80+=+.4+\"$
\n" ); document.write( " $\"+32+=+32+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );