Question

If A and B be mutually exclusive events associated with a random experiment such that P(A) = 0.4 and P(B) = 0.5, then find 

P (A ∪ B)

Answer 1

Given:
P(A) = 0.4 and P(B) = 0.5 
If A and B be mutually exclusive event, then P (A ∩ B) = 0

By addition theorem, we have:
P (A ∪ B) = P(A) + P (B) - P (A ∩ B)
                 = 0.4 + 0.5 - 0 = 0.9