Answer:
0.3333 = 33.33% probability that this red ball is from box A.
Step-by-step explanation:
Conditional Probability
We use the conditional probability formula to solve this question. It is
[tex]P(B|A) = \frac{P(A \cap B)}{P(A)}[/tex]
In which
P(B|A) is the probability of event B happening, given that A happened.
[tex]P(A \cap B)[/tex] is the probability of both A and B happening.
P(A) is the probability of A happening.
In this question:
Event A: Red ball
Event B: From box A.
Probability of a red ball:
3/10 = 0.3 of 1/2 = 0.5(box A)
6/10 = 0.6 of 1/2 = 0.5(box B). So
[tex]P(A) = 0.3*0.5 + 0.6*0.5 = 0.45[/tex]
Probability of a red ball from box A:
0.3 of 0.5, so:
[tex]P(A \cap B) = 0.3*0.5 = 0.15[/tex]
What is the probability that this red ball is from box A?
[tex]P(B|A) = \frac{P(A \cap B)}{P(A)} = \frac{0.15}{0.45} = 0.3333[/tex]
0.3333 = 33.33% probability that this red ball is from box A.
