The characteristic being calculated here is the mean or the average of the data set.
To check:
(20.73 + 20.76 + 20.68 + 20.75)/4 [we divide it by 4 because there are 4 numbers]
= 82.92 / 4
= 20.73
The moles of silicon is 4.651 moles
<u><em>calculation</em></u>
The moles of silicon is calculated using Avogadro's constant
that is according to Avogadro's law
1 mole = 6.02 x 10^23 atoms
? moles = 2.80 x 10 ^24 atoms of silicon
by cross multiplication
= [ ( 1 mole x 2.80 x 10^24 atoms) / ( 6.02 x 10 ^23 atoms)]
= 4.651 moles