The average of all the prime and composite numbers up to 100 is:

51

Since 1 is neither prime not composite number .

So , Rest all number from 1 to 100 are prime or composite number.

We have ,   2 , 3 , 4  .................. , 99 , 100

Average = \(\frac{First\; term \;+\; Last \;term }{2}\) 

= \(\frac{2 + 100 }{2}\) = \(\frac{102}{2}\) 

= 51