SOLUTION: a goldsmith has two alloys of gold, the first being 70% pure and the second being 60% pure. how many ounces of the 60 pure gold must be used to make 100 ounces of an alloy which wi

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Let X be the amount of 60% pure alloy and Y be the amount of 70% pure alloy.
First, the total weight is
1.
Next, the percentage of alloy is,
2.
Let's use eq. 1 to solve for X in terms of Y,
1.

Now substitute that into eq. 2 and solve for y.
2.




From eq. 1,


Let's check the answer using eq. 2,
2.



True statement.
Good answer.
Use 40 ounces of 60% pure alloy and 60 ounces of 70% pure alloy.