To determine the mass contribution of post-1982 pennies to the weighted average mass, we need to perform the following steps:
1. Identify the number of post-1982 pennies, which is given as 12.
2. Determine the average mass of a post-1982 penny, which is 2.5 grams.
3. Calculate the total mass contributed by the post-1982 pennies by multiplying the number of pennies by their average mass.
So, the total mass of the post-1982 pennies can be calculated as follows:
[tex]\[
\text{Total mass of post-1982 pennies} = \text{Number of post-1982 pennies} \times \text{Average mass of a post-1982 penny}
\][/tex]
[tex]\[
\text{Total mass of post-1982 pennies} = 12 \times 2.5
\][/tex]
[tex]\[
\text{Total mass of post-1982 pennies} = 30.0 \text{ grams}
\][/tex]
Thus, the post-1982 pennies contribute 30.0 grams to the weighted average mass.
