Question

A single 6-sided dice is being rolled. What is the probability of rolling a 5 or an odd number?

Answer 1

S = sample space
S = set of all possible outcomes
S = {1,2,3,4,5,6}

E = event space
E = set of items we want to happen (rolling a 5, or rolling an odd number)
E = {1, 3, 5}
note: the event of "rolling a 5" is a subset of "rolling an odd number" because 5 is odd

n(S) = number of items in the sample space
n(S) = 6

n(E) = number of items in event space
n(E) = 3

Divide the values to get the probability
P(E) = n(E)/n(S)
P(E) = 3/6
P(E) = 1/2
P(E) = 0.50
P(E) = 50%

The answer in fraction form is 1/2
The answer in decimal form is 0.50
The answer as a percentage is 50%
These three values all represent the same idea, just written in different forms.

note: writing "P(E)" means "the probability of event E occurring", which I've defined as the event space above