Find the missing probability.

[tex]
P(A)=\frac{13}{20}, \quad P(A \cap B)=\frac{13}{25}, \quad P(B \mid A)=?
[/tex]

A. [tex]\frac{4}{5}[/tex]
B. [tex]\frac{21}{100}[/tex]
C. [tex]\frac{1}{5}[/tex]
D. [tex]\frac{1}{4}[/tex]



Answer :

To determine the conditional probability [tex]\( P(B \mid A) \)[/tex], we use the following formula:

[tex]\[ P(B \mid A) = \frac{P(A \cap B)}{P(A)} \][/tex]

Given the probabilities:
[tex]\[ P(A) = \frac{13}{20} \][/tex]
[tex]\[ P(A \cap B) = \frac{13}{25} \][/tex]

We substitute these values into the formula:

[tex]\[ P(B \mid A) = \frac{P(A \cap B)}{P(A)} = \frac{\frac{13}{25}}{\frac{13}{20}} \][/tex]

To simplify this division of fractions, we multiply the numerator by the reciprocal of the denominator:

[tex]\[ P(B \mid A) = \frac{13}{25} \times \frac{20}{13} \][/tex]

The [tex]\(13\)[/tex] in the numerator and the [tex]\(13\)[/tex] in the denominator cancel each other out:

[tex]\[ P(B \mid A) = \frac{20}{25} \][/tex]

Then we simplify [tex]\(\frac{20}{25}\)[/tex]:

[tex]\[ P(B \mid A) = \frac{4}{5} \][/tex]

Therefore, the conditional probability [tex]\( P(B \mid A) \)[/tex] is:

[tex]\[ \boxed{\frac{4}{5}} \][/tex]

Thus, the correct answer is:
A. [tex]\(\frac{4}{5}\)[/tex]