Question 1203425
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A fast and easy informal solution, if your mental arithmetic is good....<br>
The fraction of the mixture that contains the higher percentage of copper is 2/(6+2) = 2/8 = 1/4.<br>
That means the percentage of copper in the mixture is 1/4 of the way from 4% to 80%.<br>
From 4% to 80% is a difference of 76%; 1/4 of that is 19%.<br>
The percentage of copper in the mixture is 4%+19% = 23%.<br>
ANSWER: 23%<br>