document.write( "Question 954102: A given alloy contains 20% copper and 5% tin. How mmany pounds of copper and of tin must be melted with 100lb. of the given alloy to produce another alloy analyzing 30% copper and 10% tin? \n" ); document.write( "
Algebra.Com's Answer #582844 by ankor@dixie-net.com(22740)\"\" \"About 
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A given alloy contains 20% copper and 5% tin.
\n" ); document.write( " How many pounds of copper and of tin must be melted with 100lb of the given alloy to produce another alloy analyzing 30% copper and 10% tin?
\n" ); document.write( ":
\n" ); document.write( "let c = amt of copper required
\n" ); document.write( "let t = amt of tin
\n" ); document.write( "then
\n" ); document.write( "(100+c+t) = total weight of the resulting alloy
\n" ); document.write( ":
\n" ); document.write( "Find how many pounds in the original 100 lb
\n" ); document.write( ".20(100) = 20 lb of copper
\n" ); document.write( ".05(100) = 5 lb of tin
\n" ); document.write( ":
\n" ); document.write( "Write an equation for each, arrange for elimination
\n" ); document.write( "Copper
\n" ); document.write( "c + 20 = .30(100 + c + t)
\n" ); document.write( "c + 20 = 30 + .3c + .3t
\n" ); document.write( "c - .3c = 30 - 20 + .3t
\n" ); document.write( ".7c - .3t = 10
\n" ); document.write( "Tin
\n" ); document.write( "t + 5 = .10(100 + c + t)
\n" ); document.write( "t + 5 = 10 + .1c + .1t
\n" ); document.write( "t - .1t = 10 - 5 + .1c
\n" ); document.write( ".9t = 5 + .1c
\n" ); document.write( "-.1c + .9t = 5
\n" ); document.write( ":\r
\n" ); document.write( "\n" ); document.write( "Multiply the 1st equation by 3, add to the above equation
\n" ); document.write( "-.1c + .9t = 5
\n" ); document.write( "2.1c + .9t = 30
\n" ); document.write( "-----------------Adding eliminates t, find c
\n" ); document.write( "2c = 35
\n" ); document.write( "c = 35/2
\n" ); document.write( "c = 17.5 lb of copper to be added
\n" ); document.write( ":
\n" ); document.write( "find t using -.1c + .9t = 5
\n" ); document.write( "-.1(17.5) + .9t = 5
\n" ); document.write( "-1.75 + .9t = 5
\n" ); document.write( ".9t = 5 + 1.75
\n" ); document.write( ".9t = 6.75
\n" ); document.write( "t = 6.75/.9
\n" ); document.write( "t = 7.5 lb of tin required
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "See of this checks out
\n" ); document.write( "Weight of resulting alloy: 100 + 17.5 + 7.5 = 125 lb
\n" ); document.write( "Copper: .30(125) = 37.5, (20 oriiginal lbs + 17.5 lbs added)
\n" ); document.write( "Tin: .10(125) = 12.5, (5 original lbs + 7.5 lbs added
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