Union Probability Calculator — Formula
## How to Calculate Union Probability
### Formula
**P(A or B) = P(A) + P(B) - P(A and B)**
The addition rule accounts for the overlap between events A and B. If you simply add P(A) and P(B), the intersection is counted twice, so you subtract P(A and B) once. For mutually exclusive events, P(A and B) = 0.
### Formula
**P(A or B) = P(A) + P(B) - P(A and B)**
The addition rule accounts for the overlap between events A and B. If you simply add P(A) and P(B), the intersection is counted twice, so you subtract P(A and B) once. For mutually exclusive events, P(A and B) = 0.
Exemplo Resolvido
P(A) = 0.3, P(B) = 0.5, P(A and B) = 0.1. Find P(A or B).
- P(A or B) = P(A) + P(B) - P(A and B)
- P(A or B) = 0.3 + 0.5 - 0.1
- P(A or B) = 0.7
- P(Neither) = 1 - 0.7 = 0.3