What is the formula of probability?

Probability of an event = (number of favourable outcomes) / (total number of outcomes)

Probability of event 'A' is equal to (Number of Event A occurred) divided by (Total Number of Events occurred in Sample Space):

P(A) = n(A)/n(S); where 'A' is Event 'A' Occurred and 'S' is Total Number of Events in Sample Space

Rule for addition- P(AuB)=P(A)+P(B)-P(AnB)

Probability = Outcome of an event/Total number of outcomes

Number of possible outcome / Number of total outcome