The average mass of the pennies in the sample is 2.16 g.
We have a set of pennies from which 10.00% have an average mass of 2.15 g and 90.00% have an average mass of 2.156 g. The average mass (am) of the whole set is a weighted average, that considers the mass (m) and the percentage (perc) of each group. We can calculate it using the following expression.
[tex]am=\frac{\Sigma m \times perc }{100 \%} = \frac{2.15g \times 10.00\% + 2.156 g \times 90.00\% }{100\%} = 2.1554 g \approx 2.16 g[/tex]
The average mass of the pennies in the sample is 2.16 g.
You can learn more about weighted average here: https://brainly.com/question/18554478
