Answer:
the numbers on an 8-sided die are 1, 2, 3, 4, 5, 6, 7, and 8
2, 3, 5, and 7 are prime numbers
half the numbers are prime
you should roll a prime number half of the time (theoretically)
if you roll the die 100 times, you (theoretically) should get a prime number 50 times, which is half of the time