15. On October 21, 1982, the Bureau if
the Mint changed the composition of
pennies. Instead of an alloy of 95% Cu
and 5% Zn by mass, a core of 99.2 Zn
and 0.8% Cu with a thin shell of copper
was adopted. The overall composition of
the new penny was 97.6% Zn and 2.4%
Cu by mass. Assume the volume of the
individual metals that make up each
penny can be added together to give the
overall volume of the penny, and assume
each penny is the same size. (Density of
Cu = 8.96 g/cm3; density of Zn = 7.14
g/cm3) Does this account for the
difference in mass among the pennies?
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