document.write( "Question 836591: The purity of gold is measured in karats, with pure gold being 24 karats. Other purities of gold are expressed as proportional parts of pure gold. How much pure gold should be mixed with 12-karat gold to obtain 72 grams of 18-karat gold? \n" ); document.write( "
Algebra.Com's Answer #504294 by ankor@dixie-net.com(22740)\"\" \"About 
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The purity of gold is measured in karats, with pure gold being 24 karats.
\n" ); document.write( " Other purities of gold are expressed as proportional parts of pure gold.
\n" ); document.write( " How much pure gold should be mixed with 12-karat gold to obtain 72 grams of 18-karat gold?
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\n" ); document.write( "18k is halfway between 12k and 24k, therefore it would be half and half
\n" ); document.write( ":
\n" ); document.write( "But if you want use a mixture equation:
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\n" ); document.write( "If 24 karats is pure gold, then
\n" ); document.write( "18 karats = 18/24 = .75
\n" ); document.write( "12 karats = 12/25 = .50
\n" ); document.write( ":
\n" ); document.write( "let g = amt of pure gold
\n" ); document.write( "then
\n" ); document.write( "(72-g) = amt of 12 karat gold
\n" ); document.write( ":
\n" ); document.write( "The mixture equation
\n" ); document.write( ".50(72-g) + g = .75(72)
\n" ); document.write( "36 - .5g + g = 54
\n" ); document.write( "-.5g + g = 54 - 36
\n" ); document.write( ".5g = 18
\n" ); document.write( "g = 18/.5
\n" ); document.write( "g = 36 grams of pure gold
\n" ); document.write( "and
\n" ); document.write( "72 - 36 = 36 grams of 12 karat gold
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