A metal recycling plant has some scrap metal that is 53% copper. It also has some other scrap metal that is 33% copper. The scrap metal is melted together and produces 1420 g of metal that is 47% copper. How many grams of the 33% copper metal was mixed with the 53% copper metal?
[A] 469 g [B] 426 g [C] 994 g [D] 1420 g
Let the amount of 53% copper to be mixed, be F
Then the amount of 33% to be mixed = 1,420 - F
We then get: .53F + .33(1,420 - F) = .47(1,420)
.53F + .33(1,420) - .33F = .47(1,420)
.2F = .47(1,420) - .33(1,420)
.2F = .14(1,420)
Amount of 53% copper to mix, or 
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