The first 15 prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 41, 43, 47, 53, 59
The average of the first 15 prime numbers is:
( 2+3+5+7+11+13+17+19+23+29+41+43+47+ 53+ 59)/15= 316.9