It is given that events A and B of an experiment are such that P(A / B...
To find: P(A) and P(B)
Solution:
We can use Bayes' theorem to find P(A) and P(B).
Bayes' theorem states that:
P(A / B) = P(B / A) x P(A) / P(B)
Substituting the given values, we get:
1 / 4 = (1 / 12) x P(A) / P(B)
Multiplying both sides by P(B), we get:
P(B) / 4 = P(A) / 12
Cross-multiplying, we get:
3P(B) = 4P(A)
Also, we know that:
P(A / B) x P(B) = P(A and B)
Substituting the given values, we get:
1 / 4 x P(B) = P(A and B)
Multiplying both sides by 4, we get:
P(B) = 4P(A and B)
Substituting this value in the equation 3P(B) = 4P(A), we get:
3(4P(A and B)) = 4P(A)
Simplifying, we get:
P(A and B) = 4P(A) / 12
P(A and B) = P(A) / 3
Now, we know that:
P(A and B) + P(A' and B) = P(B)
where A' is the complement of A.
Substituting the values, we get:
P(A) / 3 + P(B / A') x P(A') = P(B)
We are not given P(B / A'), but we do know that P(A and B') = 0, since events A and B are not independent.
Using the formula for conditional probability, we get:
P(A and B') = P(B') x P(A / B')
Since P(A and B') = 0, we get:
P(B') x P(A / B') = 0
This implies that either P(B') = 0 (which is not possible since the chance of occurrence of an event cannot be zero) or P(A / B') = 0.
If P(A / B') = 0, then events A and B' are independent, which contradicts the given information that events A and B are not independent.
Therefore, we can conclude that P(B / A') = 0.
Substituting this value in the equation above, we get:
P(A) / 3 + 0 x P(A') = P(B)
Simplifying, we get:
P(A) / 3 = P(B)
Substituting this value in the equation 3P(B) = 4P(A), we get:
3P(A) / 3 = 4P(A) / 4
Simplifying, we get:
P(A) = 3/7
Substituting this value in the equation P(A) / 3 = P(B), we get:
P(B) = 1/7
Therefore, the required probabilities are:
P(A) = 3/7
P(B) = 1/7
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