Question

Consider a piece of gold jewelry that weighs 9.81 g and has a volume of 0.670 cm3. The jewelry contains only gold and silver, which have densities of 19.3 g/cm3 and 10.5 g/cm3, respectively. Assuming that the total volume of the jewelry is the sum of the volumes of the gold and silver that it contains, calculate the percentage of gold (by mass) in the jewelry.

Answer 1

Let x = mass Au,
then 9.81-x = mass Ag.
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(1)--volume Au = m/d = x/19.3
(2)--volume Ag = m/d = (9.81-x)/10.5
(3)--volume Au + volume Ag = 0.670
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Substitute (1) and (2) into (3), solve for x and 9.81-x, then
mass % Au = (mass Au/9.81)*100 = ?
mass % Ag = (mass Ag/9.81)*100 = ?
Post your work if you get stuck.

Answer 2

How do you find x? I understand how to set up the problem, but I don't know how to get x.