Question 971955
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Two other tutors have provided essentially identical solutions using the standard formal algebraic method for solving 2-part mixture problems like this.<br>
Here is a solution using a less formal method that can be used to solve any problem like this.  The method can be especially fast and easy, especially if the numbers in the problem are "nice".<br>
(1) Use a number line if it helps to observe/calculate that 51% is 21/50 of the way from 30% to 80%.
(2) That means 21/50 of the mixture should be the alloy that is 80% copper.<br>
21/50 of 60 kg is (.42)(60) = 25.2 kg.<br>
ANSWER: 25.2 kg of the 80% copper alloy and (60-25.2)=34.8 kg of the 30% copper alloy.<br>