SOLUTION: A jeweler melts down 90 grams of jewelry that is made of an alloy of 20% silver and 80% gold. He wishes to add enough silver to create an alloy that is 30% silver and 70% gold. How

Question 214702: A jeweler melts down 90 grams of jewelry that is made of an alloy of 20% silver and 80% gold. He wishes to add enough silver to create an alloy that is 30% silver and 70% gold. How much silver should he add?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A jeweler melts down 90 grams of jewelry that is made of an alloy of 20% silver and 80% gold.
He wishes to add enough silver to create an alloy that is 30% silver and 70% gold.
How much silver should he add?
;
Write the equations in terms of % silver
:
Let x = amt of pure silver to be added to do this
:
.2(90) + x = .3(90+x)
18 + x = 27 + .3x
x - .3x = 27 - 18
.7x = 9
x =
x = 12.857 gr of pure silver required
;
:
Check solution by finding the gold amt (should be unchanged)
.8(90) = .7(90+12.857)
72 = .7(102.857)
72 = 72

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