document.write( "Question 365004: pure acid is to be added to a 10% acid solution to obtain 90l of 75% solution? what amounts should each be used? \n" ); document.write( "

Algebra.Com's Answer #260237 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"a\"$ = liters of pure acid to be added
\n" ); document.write( "Let $\"b\"$ = liters of 10% acid solution to be added
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"a+%2B+b+=+90\"$
\n" ); document.write( "(2) $\"%28a+%2B+.1b%29%2F90+=+.75\"$
\n" ); document.write( "----------------------
\n" ); document.write( "From (2):
\n" ); document.write( "(2) $\"a+%2B++.1b+=+67.5\"$
\n" ); document.write( "(2) $\"10a+%2B+b+=+675\"$
\n" ); document.write( "Subtract (1) from (2)
\n" ); document.write( "(2) $\"10a+%2B+b+=+675\"$
\n" ); document.write( "(1) $\"-a+-+b+=+-90\"$
\n" ); document.write( " $\"9a+=+585\"$
\n" ); document.write( " $\"a+=+65\"$
\n" ); document.write( "And, since
\n" ); document.write( " $\"a+%2B+b+=+90\"$
\n" ); document.write( " $\"65+%2B+b+=+90\"$
\n" ); document.write( " $\"b+=+25\"$
\n" ); document.write( "65 liters of pure acid and 25 liters of 10% solution are needed
\n" ); document.write( "check answer:
\n" ); document.write( " $\"%28a+%2B+.1b%29%2F90+=+.75\"$
\n" ); document.write( " $\"%2865+%2B+.1%2A25%29%2F90+=+.75\"$
\n" ); document.write( " $\"67.5%2F90+=+.75\"$
\n" ); document.write( " $\"67.5+=+.75%2A90\"$
\n" ); document.write( " $\"67.5+=+67.5\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );