CMA Foundation · Fundamentals of Business Mathematics and Statistics · Probability
For three events A, B and C: P(A)=0.5, P(B)=0.4, P(C)=0.3, P(A and B)=0.2, P(B and C)=0.1, P(A and C)=0.15 and P(A and B and C)=0.05. What is P(A or B or C)?
P(A or B or C) is 0.80. Sum the single probabilities to get 1.2, subtract the three pairwise intersections totalling 0.45, then add back the triple intersection 0.05, giving 0.80.
- A0.80Correct
- B0.75
- C0.85
- D0.90
Explanation
P(A or B or C) = 0.5+0.4+0.3 - (0.2+0.1+0.15) + 0.05 = 1.2 - 0.45 + 0.05 = 0.80. The option 0.75 comes from omitting the triple-intersection term. The option 0.85 comes from subtracting only two of the pairwise terms.
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