A person weighed 15 pennies on a balance and recorded the following masses: 3.112 3.109 3.059
2.467 3.079 2.518
3.129 2.545 3.050
3.053 3.054 3.072
3.081 3.131 3.064
Curious about the results, he looked at the dates on each penny. Two of the light pennies were minted in 1983 and one in 1982. The dates on the 12 heavier pennies ranged from 1970 to 1982. Two of the 12 heavier pennies were minted in 1982.
a. Do you think the Bureau of the Mint changed the way it made pennies? Explain.
b. The person calculated the average mass of the 12 heavy pennies. He expressed this average as $3.0828 g + 0.0482 $ . What is wrong with the numbers in this result, and how should the value be expressed?

A)  yes

B) The average mass of 12 pennies should be expressed as

( 3.131 + 3.129 + X12 ) g /  12

where X12 = is the mass of the 12th penny

Explanation:

A) I think the the Bureau of Mint changed the way it made pennies because from the experiment and observation carried out on 15 different pennies it can be seen that they had different weights and this difference is associated with the period/time of production of the different pennies,

B ) The average mass of any object should be expressed in the si unit of mass and not having ($) sign attached to the value instead it should be expressed in grams or kilograms (s.i unit of mass )

The average mass of 12 pennies should be expressed as

( 3.131 + 3.129 + X12 ) g /  12

where X12 = is the mass of the 12th penny

the correct answer is a

- lead + phosphoric acid = hydrogen + lead(ii) phosphate