# probability formulas

**Probability** is the branch of mathematics which deals with the study of random phenomenons and probability of occurrence of events.

Some basic** probability formulas** are:

Notations use in Probability:

= probability of event A.

= probability of event A or B.

= probability of event A and B.

Probability Formulas:

1. Probability of an event “A” is:

= (Number of outcomes favorable to “A”) ÷ (Total numbers of outcomes)

2. For any two events “A” and “B” :

3. For any three events “A” , “B” and “C”:

4. For mutually exclusive events “A” , “B” and “C” ( or if and

and

5. For two independent events “A” and “B”:

and

6. If is the event complimentary to “A” then:

7. If the occurrence of event “A” is dependent on the occurrence of event “B” then:

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