document.write( "Question 710335: How much of Brand A fruit punch (45 % fruit juice) must be mixed with 2 gal. of Brand B fruit punch (35% fruit juice) to create a mixture containing 43% fruit juice? \n" ); document.write( "
Algebra.Com's Answer #436980 by josgarithmetic(39618)\"\" \"About 
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Let's analyze the problem and put everything into variables.\r
\n" ); document.write( "\n" ); document.write( "Low concentration L=35%
\n" ); document.write( "High concentration H=45%
\n" ); document.write( "Target fruit juice concentration T=43%
\n" ); document.write( "Amount of low juice conc. punch u= 2 gallons
\n" ); document.write( "Amount of high conc. punch v = unknown
\n" ); document.write( "Amount of punch mixture M = also unknown\r
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\n" ); document.write( "\n" ); document.write( "Note that u+v=M. Using this in the concentration's rational equation will be best this way.\r
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\n" ); document.write( "\n" ); document.write( "We need this equation:
\n" ); document.write( "\"%28uL%2BvH%29%2F%28u%2Bv%29=T\"
\n" ); document.write( "Our variable to solve for is v.\r
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\n" ); document.write( "\n" ); document.write( "uL+vH=T(u+v)
\n" ); document.write( "uL+vH=Tu+Tv
\n" ); document.write( "vH-Tv+uL=Tu
\n" ); document.write( "vH-vT=uT-uL
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\n" ); document.write( "\"highlight%28v=u%28T-L%29%2F%28H-T%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now, just substitute the given values into that formula for v and compute. That will be the volume in gallons of Brand A to add to the 2 gallons of Brand B punch. Be aware in practice you might want to know 128 fluid ounces per gallon.
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