document.write( "Question 1108002: A metalworker has a metal alloy that is 20% copper and another alloy that is 70% copper. How many kilograms of each alloy should the metalworker combine to create 90 kg of a 50% copper alloy? \n" ); document.write( "

Algebra.Com's Answer #723030 by stanbon(75887) $\"\"$ $\"About$

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A metalworker has a metal alloy that is 20% copper and another alloy that is 70% copper. How many kilograms of each alloy should the metalworker combine to create 90 kg of a 50% copper alloy?
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\n" ); document.write( "Quantity Eq:: t + s = 90 kg
\n" ); document.write( "Copper Eq:: 0.2t+0.7s = 0.5*90
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\n" ); document.write( "Modify::
\n" ); document.write( "t + s = 90
\n" ); document.write( "2t + 7s = 5*90
\n" ); document.write( "--------
\n" ); document.write( "Modify for elimination::
\n" ); document.write( "2t + 2s = 2*90
\n" ); document.write( "2t + 7s = 5*90
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\n" ); document.write( "Subtract and solve for \"s\":
\n" ); document.write( "5s = 3*90
\n" ); document.write( "s = 3*18
\n" ); document.write( "s = 54 kg (amt. of 7% alloy needed)
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\n" ); document.write( "t = 90-s = 36 kg (amt. of 20% alloy needed)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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