Answer:
1/3
Step-by-step explanation:
Assuming the die is 6-sided and fair (i.e. every number has an equal chance of coming up), the chance of throwing any individual number is 1/6.
So, the chance of rolling a 1 or 5 on any given throw is 1/6 + 1/6 = 2/6 which we can simplify to 1/3.
