posted by Arthur .
'Copper' pennies actually contain very little copper. If a penny contains 91.768 % of its total volume zinc and 8.232 % of its total volume copper, what is its density? (d of Cu = 8.95 g/cm3; d of Zn = 7.14 g/cm3.)
Assume you had 100cm^3 of pennies.
Then you would have a mass of 91.768*densityzinc, and a mass of 8.232*density copper. Add those to get the total mass. You know the mass, so
find density (mass/volume)