document.write( "Question 114687: How much of an alloy that is 20% copper should be mixed with 400 ounces of an alloy that is 70% copper in order to get an alloy that is 30% copper? \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "____ ounces \n" ); document.write( "
Algebra.Com's Answer #83533 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
How much of an alloy that is 20% copper should be mixed with 400 ounces of an alloy that is 70% copper in order to get an alloy that is 30% copper?
\n" ); document.write( ":
\n" ); document.write( "Let x = amt of 20% copper is required:
\n" ); document.write( "Then
\n" ); document.write( "The resulting amt = (x+400)
\n" ); document.write( ":
\n" ); document.write( ".70(400) + .20(x) = .30(x+400)
\n" ); document.write( ":
\n" ); document.write( "280 + .2x = .3x + 120
\n" ); document.write( ":
\n" ); document.write( ".2x - .3x = 120 - 280
\n" ); document.write( ":
\n" ); document.write( "-.1x = -160
\n" ); document.write( ":
\n" ); document.write( "x = -160/-.1
\n" ); document.write( ":
\n" ); document.write( "x = +1600 oz of 20% copper is required
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check solution:
\n" ); document.write( ".7(400) + .2(1600) = .3(1600 + 400)
\n" ); document.write( "280 + 320 = .3(2000)
\n" ); document.write( "600 = 600; confirms out solution \n" ); document.write( "
\n" );