- CFA Exams
- 2021 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**

Roll a die and flip a coin, P(5 OR heads) = ______.

B. 1/12

C. 7/12

A. 5/12

B. 1/12

C. 7/12

Correct Answer: C

P(5 or heads) = P(5) + P(heads) - P(5 and heads) = 7/12

P(5) = 1/6, P(heads) = 1/2, P(A and heads) = 1/6 x 1/2 = 1/12

P(5 or heads) = P(5) + P(heads) - P(5 and heads) = 7/12

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**User Contributed Comments**
6

User |
Comment |
---|---|

eejo |
1/6 + 1/2 -1/12= 2/12 + 6/12 - 1/12= 8/12-1/12= 7/12 |

morek |
why are these not mutually exclusive? |

Vikku |
morek, bcoz they are independent events. A 5 & a head, both can happen together. |

olagbami |
@ morek....p(5 and head) is greater than zero, so they are both mutually exclusive events. |

khalifa92 |
mutually exclusive not- |

Mheaton37 |
Heads is a 50% chance, adding another event on top of that with "or" would mean 5/12 and 1/12 are automatically eliminated as answers. |