SOLUTION: A goldsmith has two gold alloys. The first alloy is 40% gold; the second alloy is 70% gold. How many grams of each should be mixed to produce 30 grams of an alloy that is 60% gold?

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Question 1130534: A goldsmith has two gold alloys. The first alloy is 40% gold; the second alloy is 70% gold. How many grams of each should be mixed to produce 30 grams of an alloy that is 60% gold?
amount of 40% gold g
amount of 70% gold g
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
x grams of the 70% Gold
30-x grams of the 40% Gold

70x%2B40%2830-x%29=60%2A30
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7x%2B4%2830-x%29=180
7x%2B120-4x=180
3x=180-120
3x=60
x=20
.
.
You are not missing how to get the 40%. Look again at the assigned variable. x if for grams of the 70% Gold. What else did THAT mean? The problem description itself should help.
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30-x grams of the 40% Gold
30-20
10--------amount of the 40% Gold alloy