Probability Formula

Probability in mathematics helps to find the likelihood of an events occurrence. It can be calculated for single event and multiple events. For Single Event, there are two probability formulas, to find the possibility of event occurrence and impossibility of the event occurrence. To find the probability, divide the possible number of events to happen by total number of events. While the impossibility of the event can be found by subtracting the possible probability by one.

Single Event Probability Formula :

Probability of event A that occurs P(A) = n(A) / n(S).
Probability of event A that does not occur P(A) = 1 - P(A).

Multiple Event Probability Formula :

P(A) = n(A) / n(S).
P(A) = 1 - P(A).
P(B) = n(B) / n(S).
P(B) = 1 - P(B).
Probability that both the events occur P(A ∩ B) = P(A) x P(B).
Probability that either of event occurs P(A ∪ B) = P(A) + P(B) - P(A ∩ B).
Conditional Probability P(A | B) = P(A ∩ B) / P(B).


n(A) - Number of Occurrence in Event A,
n(B) - Number of Occurrence in Event B,
n(S) - Total Number of Possible Outcomes.

Related Calculator:

english Calculators and Converters

Ask a Question