0≤P(A)≤10 \le P(A) \le 10≤P(A)≤1; P(S)=1P(S) = 1P(S)=1; for mutually exclusive A,BA, BA,B: P(A∪B)=P(A)+P(B)P(A \cup B) = P(A) + P(B)P(A∪B)=P(A)+P(B).