If you were asked to calculate the density of a penny, you might have difficulty because

Question

the small amount of water displaced by one penny. How could you modify the
procedure to go about calculating the density of a penny?

Answer 1

"............small amount of water displaced by one penny ......."
So bust the piggy bank and use 100 pennies.

Answer 2

but make sure all of the pennies are the same kind; i.e., old pennies were copper and new pennies are copper clad zinc.