Question

There are two mutually exclusive events A and B with P(A) =0.5 and P(B) = 0.4. Find the probability when a and b does not occur

Answer 1

since A and B are mutually exclusive, therefore A intersection B is ∅. 

Hence, P( A ∪ B ) = P(A) + P(B). 

hence, P(A∪B) = 0.5 + 0.4 = 0.9

Now, P(A' ∩ B') = P(A∪B)' [ using DeMorgan's Law ]

= 1 - P(A∪B) = 1-0.9 = 0.1