Question

P(A) = 0.8, P(B) = 0.55 and P(A and B) = 0.35.
What is P(A or B)?

Answer 1

Answer:  1

Work Shown:

P(A or B) = P(A) + P(B) - P(A and B)

P(A or B) = 0.8 + 0.55 - 0.35

P(A or B) = 1.35 - 0.35

P(A or B) = 1

A probability of 1 means there is 100% certainty the event happens. This must mean that there are only possible outcomes are: either event A happens, or B happens, or possibly both A and B happen simultaneously.