document.write( "Question 629214: Rx: zink oxide 20% ointment 90g. how many grams of zink oxide 40% ointment and zink oxide 10% ointment should you mix to prepare the prescription. \n" ); document.write( "

Algebra.Com's Answer #396099 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = grams of 40% ointment needed
\n" ); document.write( "Let $\"+b+\"$ = grams of 10% ointment needed
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+a+%2B+b+=+90+\"$
\n" ); document.write( "(2) $\"+%28+.4a+%2B+.1b+%29+%2F+90+=+.2+\"$
\n" ); document.write( "-------------------------
\n" ); document.write( "(2) $\"+.4a+%2B+.1b+=+.2%2A90+\"$
\n" ); document.write( "(2) $\"+.4a+%2B+.1b+=+18+\"$
\n" ); document.write( "(2) $\"+4a+%2B+b+=+180+\"$
\n" ); document.write( "Subtract (1) from (2)
\n" ); document.write( "(2) $\"+4a+%2B+b+=+180+\"$
\n" ); document.write( "(1) $\"+-a+-+b+=+-90+\"$
\n" ); document.write( " $\"+3a+=+90+\"$
\n" ); document.write( " $\"+a+=+30+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+a+%2B+b+=+90+\"$
\n" ); document.write( "(1) $\"+30+%2B+b+=+90+\"$
\n" ); document.write( "(1) $\"+b+=+60+\"$
\n" ); document.write( "30 grams of 40% ointment are needed
\n" ); document.write( "60 grams of 10% ointment are needed
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+%28+.4%2A30+%2B+.1%2A60+%29+%2F+90+=+.2+\"$
\n" ); document.write( "(2) $\"+%28+12+%2B+6+%29+%2F+90+=+.2+\"$
\n" ); document.write( "(2) $\"+18%2F90+=+.2+\"$
\n" ); document.write( "(2) $\"+18+=+18+\"$
\n" ); document.write( "OK \n" ); document.write( "

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