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

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