The term “test” for precious metal alloys means the content of the precious metal in 1000 grams of the alloy. For example, the fineness of silver 925 indicates the presence in 1000 of the alloy only 925 of pure silver. The rest is other metals.
To solve our problem, we calculate the mass of the obtained alloy and calculate the sample through the simplest proportion.
m = 400 + 45 = 445 g is the mass of an alloy of gold with copper
Now let’s make the proportion:
400 g of gold is contained in 445 g of alloy, and
x g of gold is contained in 1000 g of alloy
X = (1000 * 400) / 445 = 898.9 g of gold in 1000 g of alloy. The fineness of the gold alloy is the same.
Answer: fineness of gold alloy 898.9
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