Question 63752
A metal alloy is 25% copper. Another metal alloy is 50% copper. How much of each alloy should be mixed to create 1000 grams of an alloy that is 45% copper?
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Let amount of 25% alloy be "x" ; amount of copper in it is 0.25x grams
Amount of 50% alloy is "1000-x" ; 
amount of copper is 0.5(1000-x)=500-0.5x grams
Amount of mixture is 1000 grams; amount of copper is .45(1000)=450 grams
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EQUATION:
copper + copper = copper
0.25x+500-0.5x=450
-0.25x=-50
x=200 grams (amount of 25% alloy)
1000-x=800 grams (amount of 50% alloy)
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Cheers,
Stan H.