Find the missing probability.

[tex]
P(A)=\frac{2}{5}, \ P(B \mid A)=\frac{9}{20}, \ P(A \cap B)= \text{ ? }
[/tex]

A. [tex]\frac{7}{50}[/tex]

B. [tex]\frac{7}{10}[/tex]

C. [tex]\frac{33}{100}[/tex]

D. [tex]\frac{9}{50}[/tex]



Answer :

Sure, let's find [tex]\( P(A \cap B) \)[/tex] using the given probabilities.

We know:
- [tex]\( P(A) = \frac{2}{5} \)[/tex]
- [tex]\( P(B \mid A) = \frac{9}{20} \)[/tex]

To find [tex]\( P(A \cap B) \)[/tex], we use the definition of conditional probability, which is given by:

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

Rearranging this formula to solve for [tex]\( P(A \cap B) \)[/tex], we get:

[tex]\[ P(A \cap B) = P(B \mid A) \cdot P(A) \][/tex]

Substitute the given values into this formula:

[tex]\[ P(A \cap B) = \frac{9}{20} \cdot \frac{2}{5} \][/tex]

To multiply the fractions, multiply the numerators together and the denominators together:

[tex]\[ P(A \cap B) = \frac{9 \times 2}{20 \times 5} \][/tex]

[tex]\[ P(A \cap B) = \frac{18}{100} \][/tex]

Simplifying [tex]\( \frac{18}{100} \)[/tex] gives:

[tex]\[ P(A \cap B) = \frac{9}{50} \][/tex]

Thus, the missing probability [tex]\( P(A \cap B) \)[/tex] is [tex]\( \frac{9}{50} \)[/tex], which corresponds to option D.