Question 190409

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