Question

A collection of pennies was investigated. 10.00% were found to have been minted in San Francisco with an average mass of 2.15 g and 90.00% we’re minted in in Philly with an average mass of 2.156 g. What was the average mass of pennies in this sample? Give the correct answer with the proper amount of significant figures

Answer 1

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.

$am=\frac{\Sigma m \times perc }{100 \%} = \frac{2.15g \times 10.00\% + 2.156 g \times 90.00\% }{100\%} = 2.1554 g \approx 2.16 g$

The average mass of the pennies in the sample is 2.16 g.

You can learn more about weighted average here: brainly.com/question/18554478