Question 971955
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A metal worker has a metal alloy that is 30% copper and another alloy that is 80% copper. 
How many kilograms of each alloy should the metalworker combine to create 60 kilograms of a 51% copper alloy?
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        The solution and the answer in the post by @lwsshak3 are incorrect due to arithmetic error.

        See my correct solution below.



let x=amt of 30% copper alloy to combine
60-x=amt of 80% copper alloy to combine
..
0.3x + 0.8*(60-x) = 0.51*60
0.3x + 48 - 0.8x = 30.6
48 - 30.6 = 0.8x - 0.3x
0.50x = 17.4
x = 34.8
How many kilograms of each alloy should the metalworker combine?
30% copper alloy: 34.8 kg
80% copper alloy: 60-34.8 = 25.2 kg


<U>CHECK</U> &nbsp;for the final concentration  &nbsp;&nbsp;{{{(0.3*34.8+0.8*25.2)/(34.8+25.2)}}} = 0.51.  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;! precisely correct !


Solved.