SOLUTION: An alloy of silver and gold is recast with an addition of silver. The first alloy is 80 oz, 10 oz. is gold. If the new alloy is to have only 1/5 oz of gold in every 5 oz. how muc

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Question 190409: An alloy of silver and gold is recast with an addition of silver. The first alloy is 80 oz, 10 oz. is gold. If the new alloy is to have only 1/5 oz of gold in every 5 oz. how much silver must be added?
I am really having trouble with this. Would you please help? Thanks so much.
Answer by ptaylor(2198) (Show Source):
You can put this solution on YOUR website!

Let x=amount of silver that needs to be added
Amount of gold before silver is added=amount of gold after silver is added;
so our equation to solve is:
10=(1/25)(80+x)
(Where does the 1/25 come from? Well 1/5 oz of gold for every 5 oz of alloy is the same as 1/25 oz of gold for every oz of alloy and we have 80+x ounces of alloy)---but we could, as well, write the equation as follows:
10=(1/5)((80+x)/5)
Multiply each side by 25
250=80+x subtract 80 from each side
x=170 oz --------------amount of silver that needes to be added
CK
10=(1/25)(80+170)
10=(1/25)(250)
10=10

Hope this helps----ptaylor