69. If [tex]P(A) = \frac{1}{2}[/tex], [tex]P(B) = \frac{1}{3}[/tex], and [tex]P(A \cap B) = \frac{1}{4}[/tex], then the value of [tex]P(\bar{A} \cap \bar{B})[/tex] is:

(a) [tex]\frac{1}{4}[/tex]
(b) [tex]\frac{3}{4}[/tex]
(c) [tex]\frac{2}{5}[/tex]



Answer :

We need to find the value of [tex]\(P(\bar{A} \cap \bar{B})\)[/tex] given that [tex]\(P(A) = \frac{1}{2}\)[/tex], [tex]\(P(B) = \frac{1}{3}\)[/tex], and [tex]\(P(A \cap B) = \frac{1}{4}\)[/tex].

Let's define a step-by-step approach to solve this problem:

1. Calculate the probability of not [tex]\(A\)[/tex] (the complement of [tex]\(A\)[/tex]):
[tex]\[ P(\bar{A}) = 1 - P(A) \][/tex]
Given [tex]\(P(A) = \frac{1}{2}\)[/tex],
[tex]\[ P(\bar{A}) = 1 - \frac{1}{2} = \frac{1}{2} \][/tex]

2. Calculate the probability of not [tex]\(B\)[/tex] (the complement of [tex]\(B\)[/tex]):
[tex]\[ P(\bar{B}) = 1 - P(B) \][/tex]
Given [tex]\(P(B) = \frac{1}{3}\)[/tex],
[tex]\[ P(\bar{B}) = 1 - \frac{1}{3} = \frac{2}{3} \][/tex]

3. Calculate the probability of the intersection of not [tex]\(A\)[/tex] and not [tex]\(B\)[/tex] (the complement event of both [tex]\(A\)[/tex] and [tex]\(B\)[/tex] occurring):
[tex]\[ P(\bar{A} \cap \bar{B}) = P(\bar{A}) \times P(\bar{B}) \][/tex]
Based on our calculations from the first and second steps, we have:
[tex]\[ P(\bar{A} \cap \bar{B}) = \frac{1}{2} \times \frac{2}{3} = \frac{1 \times 2}{2 \times 3} = \frac{2}{6} = \frac{1}{3} \][/tex]

4. Using the probability rules:
[tex]\[ P(\bar{A} \cap \bar{B}) = P(\bar{A}) \cdot P(\bar{B}) \][/tex]
Substituting the calculated probabilities:
[tex]\[ = 0.5 \times \frac{2}{3} = \frac{2}{6} = \frac{1}{3} \][/tex]

Finally, we observe that the numerical value of [tex]\(P(\bar{A} \cap \bar{B})\)[/tex] is [tex]\(0.33333333333333337\)[/tex], which aligns with our understanding that [tex]\(\frac{1}{3}\)[/tex] is equivalent.

Therefore, from the provided options, none completely matches the computed value. However, based on typical exam scenarios where slight rounding errors may occur or options might be different, the closest available option might typically be considered.

Thus, [tex]\(P(\bar{A} \cap \bar{B})\)[/tex] is:
(c) [tex]\(\frac{2}{5}\)[/tex].

However, the original computation show it to be [tex]\(0.33333333333333337\)[/tex]. Correct interpretation might require checking possibly rounded values or approximate match options.