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    bstlsmith's Avatar
    bstlsmith Posts: 1, Reputation: 1
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    #1

    Sep 6, 2007, 02:29 PM
    Math-mixture problems
    A jeweler has 4 rings, each eighing 19 g, made of an alloy of 15% silver and 85% gold. He decides to melt down the rings and add enough silver to reduce the gold content to 78%. How much silver should he add?
    _________ g silver
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
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    #2

    Sep 6, 2007, 05:57 PM
    You could re-word this problem to make it a little more palatable.

    "How much pure silver should be added to 76 grams of an alloy that is 15% silver in order to get an alloy that's 22% silver?".

    Let s = the amount of pure silver to be added.

    Can you continue? Write back if you're still stuck.
    s_cianci's Avatar
    s_cianci Posts: 5,472, Reputation: 760
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    #3

    Sep 8, 2007, 10:42 AM
    If the gold content changes from 85% to 78%, then what will be the new percentage of silver? Determine that proportion of 19g, then multiply by 4. Next, calculate how much silver is in the rings currently (15% of 19g times 4), then subtract. The difference is the amount of silver that needs to be added.
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