Physics(class) /Math (problem)
posted by Toulouse .
Joe has a ring weighing 16 grams made of an alloy of 20% silver and the rest gold. He decides to melt down the rings and add enough silver to reduce the gold content to 69% . How many grams of silver should he add?

considering just the mass of the silver,
(.20)(16)+x = (.31)(16+x)
x =2.55
so, add 2.55g of silver
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