Probability is calculated by comparing the odds to a certain event occurring to the number of possible events.
P=[tex] \frac{possibility-of-an-event-occuring}{number-of-total-outcomes} [/tex]
For example, take a six-sided dice number 1-6 on each side. The probability of rolling a 4 would be1 in 6 or 1/6. This is because of the six possible outcomes, rolling a 4 is only one of them.
P(4)=1/6
Now take the same dice. The probability of rolling an even number is 3/6. To see why, lets look at the total possible outcomes:
1
2
3
4
5
6
Of the 6 possibilities, 3 are even numbers.
P(even)=3/6 or 1/2
