Question

Event B is dependent on event A, and event A occurs before event B. Which expression is equal to the probability of event A?

Answer 1

Answer:

$P(A)=\frac{P(B\cap \: A)}{P(B|A)}$

Step-by-step explanation:

Since event B is dependent on event A,

$P(B\cap\: A)\ne P(B) \times P(A)$

We also have the condition that, event A occurs before event B.

So probability of B given A is

$P(B|A)=\frac{P(B\cap \: A)}{P(A)}$

We now solve for P(A) to get:

$P(A)=\frac{P(B\cap \: A)}{P(B|A)}$