document.write( "Question 744940: three solutions contain a certain acid. the first contains 15% acid, the second 35%, and the third 40%. A chemist wishes to use all three solutions to obtain a 75-liter mixture containing 34% acid. If the chemist wants to use twice as much of the 35% solution as of the 40% solution, how many liters, to the nearest 10th, of each solution should be used? \n" ); document.write( "
Algebra.Com's Answer #453617 by josmiceli(19441)\"\" \"About 
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Let \"+a+\" = liters of 40% solution needed
\n" ); document.write( "\"+2a+\" = liters of 35% solution needed
\n" ); document.write( "Let \"+b+\" = liters of 15% solution needed
\n" ); document.write( "---------------
\n" ); document.write( "\"+.4a+\" = liters of acid in 40% solution
\n" ); document.write( "\"+.35%2A2a+=+.7a+\" = liters of acid in 35% solution
\n" ); document.write( "\"+.15b+\" = liters of acid in 15% solution
\n" ); document.write( "----------------
\n" ); document.write( "(1) \"+a+%2B+2a+%2B+b+=+75+\"
\n" ); document.write( "(2) \"+%28+.4a+%2B+.7a+%2B+.15b+%29+%2F+75+=+.34+\"
\n" ); document.write( "----------------
\n" ); document.write( "(1) \"+3a+%2B+b+=+75+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+1.1a+%2B+.15b+=+.34%2A75+\"
\n" ); document.write( "(2) \"+1.1a+%2B+.15b+=+25.5+\"
\n" ); document.write( "(2) \"+110a+%2B+15b+=+2550+\"
\n" ); document.write( "----------------
\n" ); document.write( "Multiply both sides of (1) by \"+15+\"
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) \"+110a+%2B+15b+=+2550+\"
\n" ); document.write( "(1) \"+-45a+-+15b+=+-1125+\"
\n" ); document.write( "\"+65a+=+1425+\"
\n" ); document.write( "\"+a+=+21.9+\"
\n" ); document.write( "\"+2a+=+43.8+\"
\n" ); document.write( "and, since
\n" ); document.write( "(1) \"+3a+%2B+b+=+75+\"
\n" ); document.write( "(1) \"+3%2A21.9+%2B+b+=+75+\"
\n" ); document.write( "(1) \"+65.8+%2B+b+=+75+\"
\n" ); document.write( "(1) \"+b+=+9.2+\"
\n" ); document.write( "21.9 liters of 40% solution are needed
\n" ); document.write( "43.8 liters of 35% solution needed
\n" ); document.write( "9.2 liters of 15% solution are needed
\n" ); document.write( "--------------
\n" ); document.write( "check:
\n" ); document.write( "(2) \"+%28+.4a+%2B+.7a+%2B+.15b+%29+%2F+75+=+.34+\"
\n" ); document.write( "(2) \"+%28+1.1%2A21.9+%2B+.15%2A9.2+%29+%2F+75+=+.34+\"
\n" ); document.write( "(2) \"++24.1+%2B+1.4+=+.34%2A75+\"
\n" ); document.write( "(2) \"+25.5+=+25.5+\"
\n" ); document.write( "OK
\n" ); document.write( "
\n" );