A box contains a mixture of small copper spheres and small lead spheres. The total volume of both metals is measured by the displacement of water to be 417cm3 and the total mass is 4.40kg . What percentage of the spheres are copper?

I keep getting 32.9% but that is wrong.

## Answers (1)

Density pure copper is 8.96 grams/cm3 Density of pure lead is 11.4 grams/cm3

Average density of the lead and copper balls above is 4400 grams over 417 cm3 = 10.55 grams/cm3.

Let X = the decimal fraction of lead in the mixture and l.0 minus X = the decimal fraction of copper.in the mixture

ll.4 g/cm3 (X) plus (1.0 minus X)(8.96 grams/cm3)= 10.55 grams average density

11.4 x plus 8.96 minus 8.96X = 10.55

2.44 x + 8.96 = 10.55

2.44 X = l.59

X = 1.59 over 2.44 which = .65 or 65% lead and l00% minus 65% = 35% copper.

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Reference:retired chem teacher