We are given the probabilities of events $A$, $B$, $C$, $AB$ (which means $A \cap B$), $AC$ (which means $A \cap C$), $BC$ (which means $B \cap C$), and $ABC$ (which means $A \cap B \cap C$). We are asked to find the probabilities of $A \cup B$, $\overline{AB}$ (complement of $A \cap B$), $A \cup B \cup C$, $\overline{ABC}$ (complement of $A \cap B \cap C$).

Probability and StatisticsProbabilitySet TheoryEventsUnionIntersectionComplement
2025/3/20

1. Problem Description

We are given the probabilities of events AA, BB, CC, ABAB (which means ABA \cap B), ACAC (which means ACA \cap C), BCBC (which means BCB \cap C), and ABCABC (which means ABCA \cap B \cap C). We are asked to find the probabilities of ABA \cup B, AB\overline{AB} (complement of ABA \cap B), ABCA \cup B \cup C, ABC\overline{ABC} (complement of ABCA \cap B \cap C).

2. Solution Steps

a. P(AB)P(A \cup B):
We use the formula:
P(AB)=P(A)+P(B)P(AB)P(A \cup B) = P(A) + P(B) - P(A \cap B)
P(A)=12P(A) = \frac{1}{2}
P(B)=13P(B) = \frac{1}{3}
P(AB)=P(AB)=110P(A \cap B) = P(AB) = \frac{1}{10}
P(AB)=12+13110=1530+1030330=25330=2230=1115P(A \cup B) = \frac{1}{2} + \frac{1}{3} - \frac{1}{10} = \frac{15}{30} + \frac{10}{30} - \frac{3}{30} = \frac{25-3}{30} = \frac{22}{30} = \frac{11}{15}
b. P(AB)P(\overline{AB}):
We use the formula:
P(AB)=1P(AB)P(\overline{AB}) = 1 - P(AB)
P(AB)=110P(AB) = \frac{1}{10}
P(AB)=1110=1010110=910P(\overline{AB}) = 1 - \frac{1}{10} = \frac{10}{10} - \frac{1}{10} = \frac{9}{10}
c. P(ABC)P(A \cup B \cup C):
We use the formula:
P(ABC)=P(A)+P(B)+P(C)P(AB)P(AC)P(BC)+P(ABC)P(A \cup B \cup C) = P(A) + P(B) + P(C) - P(A \cap B) - P(A \cap C) - P(B \cap C) + P(A \cap B \cap C)
P(A)=12P(A) = \frac{1}{2}
P(B)=13P(B) = \frac{1}{3}
P(C)=15P(C) = \frac{1}{5}
P(AB)=110P(A \cap B) = \frac{1}{10}
P(AC)=115P(A \cap C) = \frac{1}{15}
P(BC)=120P(B \cap C) = \frac{1}{20}
P(ABC)=130P(A \cap B \cap C) = \frac{1}{30}
P(ABC)=12+13+15110115120+130P(A \cup B \cup C) = \frac{1}{2} + \frac{1}{3} + \frac{1}{5} - \frac{1}{10} - \frac{1}{15} - \frac{1}{20} + \frac{1}{30}
P(ABC)=3060+2060+1260660460360+260P(A \cup B \cup C) = \frac{30}{60} + \frac{20}{60} + \frac{12}{60} - \frac{6}{60} - \frac{4}{60} - \frac{3}{60} + \frac{2}{60}
P(ABC)=30+20+12643+260=6413+260=51+260=5360P(A \cup B \cup C) = \frac{30 + 20 + 12 - 6 - 4 - 3 + 2}{60} = \frac{64 - 13 + 2}{60} = \frac{51 + 2}{60} = \frac{53}{60}
d. P(ABC)P(\overline{ABC}):
We use the formula:
P(ABC)=1P(ABC)P(\overline{ABC}) = 1 - P(ABC)
P(ABC)=130P(ABC) = \frac{1}{30}
P(ABC)=1130=3030130=2930P(\overline{ABC}) = 1 - \frac{1}{30} = \frac{30}{30} - \frac{1}{30} = \frac{29}{30}

3. Final Answer

P(AB)=1115P(A \cup B) = \frac{11}{15}
P(AB)=910P(\overline{AB}) = \frac{9}{10}
P(ABC)=5360P(A \cup B \cup C) = \frac{53}{60}
P(ABC)=2930P(\overline{ABC}) = \frac{29}{30}

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