The weighted average of a penny is = 67.9g
Calculation of average weight
The sample of penny for pre 1982 is a total of = 18 pennies.
The mass of each penny for pre 1982 = 3.1
Therefore the total weight for penny for pre 1982
= 18×3.1
= 55.8
The sample of penny for post 1982 is a total of = 32 pennies.
The mass of each penny for post 1982 = 2.5
Therefore the total weight for penny for post 1982
=32×2.5
= 80
The weighted average
= 55.8+80/2
= 135.8/2
= 67.9g
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