% copper in post-1982 pennies 1. The problem statement, all variables and given/known data The total mass of each penny is 2.500g, the density of copper is 8.96g/ml, the density of zinc is 7.14g/ml and the mass of a penny if it was 100% copper would be 3.11g. 2. Relevant equations 3. The attempt at a solution I am not too sure how to start this one. If someone could give me a boost I would appreciate it.