SOLUTION: A goldsmith has 120 grams of a gold alloy (a mixture of gold and one or more metals) containing 75% pure gold. How much pure gold must be added to this alloy to make it 80% pure go

Question 211309This question is from textbook College Algebra
: A goldsmith has 120 grams of a gold alloy (a mixture of gold and one or more metals) containing 75% pure gold. How much pure gold must be added to this alloy to make it 80% pure gold? This question is from textbook College Algebra

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A goldsmith has 120 grams of a gold alloy (a mixture of gold and one or more metals) containing 75% pure gold. How much pure gold must be added to this alloy to make it 80% pure gold?
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Equation:
gold + gold = gold
0.75*120 + x = 0.80(120+x)
Multiply thru by 100 to get:
75*120 + 100x = 80*120 + 80x
20x = 5*120
x = 30 grams (amt. of pure gold that must be added)
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Cheers,
Stan H.
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