We are given three independent events A, B, and C with probabilities $P(A) = \frac{1}{2}$, $P(B) = \frac{1}{3}$, and $P(C) = \frac{1}{4}$. We want to find the probability of the event $(A \cap B) \cup C$. We need to provide the answer as an irreducible fraction.

Probability and StatisticsProbabilityIndependent EventsSet TheoryProbability of UnionIrreducible Fractions
2025/5/14

1. Problem Description

We are given three independent events A, B, and C with probabilities P(A)=12P(A) = \frac{1}{2}, P(B)=13P(B) = \frac{1}{3}, and P(C)=14P(C) = \frac{1}{4}. We want to find the probability of the event (AB)C(A \cap B) \cup C. We need to provide the answer as an irreducible fraction.

2. Solution Steps

Since A, B, and C are independent events, ABA \cap B is also independent of C.
Therefore, we can use the formula for the probability of the union of two events:
P(XY)=P(X)+P(Y)P(XY)P(X \cup Y) = P(X) + P(Y) - P(X \cap Y).
In our case, X=ABX = A \cap B and Y=CY = C.
Thus, we have:
P((AB)C)=P(AB)+P(C)P((AB)C)P((A \cap B) \cup C) = P(A \cap B) + P(C) - P((A \cap B) \cap C).
Since A, B, and C are independent,
P(AB)=P(A)P(B)=1213=16P(A \cap B) = P(A)P(B) = \frac{1}{2} \cdot \frac{1}{3} = \frac{1}{6}.
Also, since A, B, and C are independent,
P((AB)C)=P(ABC)=P(A)P(B)P(C)=121314=124P((A \cap B) \cap C) = P(A \cap B \cap C) = P(A)P(B)P(C) = \frac{1}{2} \cdot \frac{1}{3} \cdot \frac{1}{4} = \frac{1}{24}.
Now we can substitute these values into the formula:
P((AB)C)=16+14124P((A \cap B) \cup C) = \frac{1}{6} + \frac{1}{4} - \frac{1}{24}.
To add these fractions, we need a common denominator, which is
2

4. $P((A \cap B) \cup C) = \frac{4}{24} + \frac{6}{24} - \frac{1}{24} = \frac{4 + 6 - 1}{24} = \frac{9}{24}$.

Now we simplify the fraction:
924=3338=38\frac{9}{24} = \frac{3 \cdot 3}{3 \cdot 8} = \frac{3}{8}.

3. Final Answer

The probability P((AB)C)P((A \cap B) \cup C) is 38\frac{3}{8}.

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