SOLUTION: A jeweler has 6 rings, each weighing 18 g, made of an alloy of 7% silver and 93% gold. She decides to melt down the rings and add enough silver to reduce the gold content to 81%. H

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Question 803293: A jeweler has 6 rings, each weighing 18 g, made of an alloy of 7% silver and 93% gold. She decides to melt down the rings and add enough silver to reduce the gold content to 81%. How much silver should she add?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Let w = grams of Silver to add, to dilute the gold.

{Amount of gold}/{Amount of alloy} = {81% or 0.81}

%2818%2A6%2A0.93%29%2F%2818%2A6%2Bw%29=0.81 to use decimal fractions instead of "percents".
18%2A6%2A0.93=0.81%2818%2A6%2Bw%29
0.81%2A18%2A6%2B0.81w=18%2A6%2A0.93
0.81w=18%2A6%2A0.93-0.81%2A18%2A6
0.81w=18%2A6%280.93-0.81%29
0.81w=0.04%2818%2A6%29
w=%280.04%2A6%2A18%29%2F0.81
w=4%2A6%2A18%2F81
w=%282%2A2%2A2%2A3%2A2%2A3%2A3%29%2F%283%2A3%2A3%2A3%29
w=%282%2A2%2A2%2A2%2A3%2A3%2A3%29%2F%283%2A3%2A3%2A3%29
highlight%28w=16%2F3=5%261%2F3%29 grams of Silver