# Although pennies are mostly composed of copper (Cu), they also contain zinc (Zn). In 1982, the density of pennies changed because the ratio of copper…

Although pennies are mostly composed of copper (Cu), they also contain zinc (Zn). In 1982, the density of pennies changed because the ratio of copper to zinc was changed. In pennies minted in 1981and prior, pennies contained 95% Cu & 5% Zn. In pennies minted since 1983, pennies contain 97.5% Zn and 2.5% Cu. The density of Cu = 8.92 g/cm3. The density of Zn = 7.14 g/cm3.

1.      Which penny should have the higher density, one minted in 1975 or one minted in 1995?

2.      Calculate the density of a penny minted in 1980. [(% Cu) * (Cu density) + (%Zn) * (Zn density)]

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3.      Calculate the density of a penny minted 1990. [(% Cu) * (Cu density) + (%Zn) * (Zn density)]