please answer this question：
when I enter school，3 ｏｆ 4 times i use the main door. when i leave school，i use the main door only 1 ｏｆ3 times. ｏｎ ａｎy given ｄａｙwhat is the proｂａｂｌｉｔｙthat i both ｅｎｔｅr and leave by the main doｏｒ？
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The events "Entering school through the main door" and "Leaving by main door" are independent. Outcome of second event does not depend on outcome of 1st event.
Label them event A and B. P(A) = 3/4 P(B) = 1/3
So P(B / A ) = P (A) * P(B) as P(A intersection B) is 0.
Answer is 3/4 * 1/3 = 1/4
Label them event A and B. P(A) = 3/4 P(B) = 1/3
So P(B / A ) = P (A) * P(B) as P(A intersection B) is 0.
Answer is 3/4 * 1/3 = 1/4
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