English

Let A and B be two events such that P(A) = 38, P(B) = 58 and P(A ∪ B) = 34. Then P(A|B).P(A′|B) is equal to ______.

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Question

Let A and B be two events such that P(A) = `3/8`, P(B) = `5/8` and P(A ∪ B) = `3/4`. Then P(A|B).P(A′|B) is equal to ______.

Options

  • `2/5`

  • `3/8`

  • `3/20`

  • `6/25`

MCQ
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Solution

Let A and B be two events such that P(A) = `3/8`, P(B) = `5/8` and P(A ∪ B) = `3/4`. Then P(A|B).P(A′|B) is equal to `6/25`.

Explanation:

Given that: P(A) = `3/8`, P(B) = `5/8` and P(A ∪ B) = `3/4`

∴ P(A ∪ B) = P(A) + P(B) – P(A ∩ B)

`3/4 = 3/8 + 5/8 - "P"("A" ∩ "B")`

⇒ P(A ∩ B) = `3/8 + 5/8 - 3/4 = 1/4`

Now `"P"("A"/"B") * "P"("A'"/"B") = ("P"("A" ∩ "B"))/("P"("B")) * ("P"("A'" ∩ "B"))/("P"("B"))`

= `("P"("A" ∩ "B"))/("P"("B")) * ("P"("B") - "P"("A" ∩ "B"))/("P"("B"))`

= `(1/4)/(5/8) * ((5/8 - 1/4))/(5/8)`

= `2/5 * 3/5`

= `6/25`

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Chapter 13: Probability - Exercise [Page 281]

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NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 13 Probability
Exercise | Q 71 | Page 281

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