- CFA Exams
- CFA Level I Exam
- Study Session 2. Quantitative Methods (1)
- Reading 8. Probability Concepts
- Subject 3. Addition Rule for Probabilities: the Probability that at Least One of Two Events Will Occur

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**CFA Practice Question**

If two events, A and B, are mutually exclusive, what does the special rule of addition state?

A. P(A and/or B) = P(A) +P(B)

B. P(A and B) = P(A) + P(B)

C. P(A or B) = P(A) + P(B)

**Explanation:**The key information is that these events are mutually exclusive. So P(A or B) = P(A) + P(B). The probabilities stand alone.

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**User Contributed Comments**
1

User |
Comment |
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praj24 |
And = multiplication Or = Addition |