JEE Main 2019 · 8 Apr · Shift I

JEE Main 2019 Mathematics question on Probability

Let AA and BB be two non-null events such that A⊂BA \subset B. Then, which of the following statements is always correct.
  1. A.
    P(A∣B)=P(B)−P(A)P(A|B) = P(B) - P(A)
  2. B.
    P(A∣B)≥P(A)P(A|B) \geq P(A)
  3. C.
    P(A∣B)≤P(A)P(A|B) \leq P(A)
  4. D.
    P(A∣B)=1P(A|B) = 1
Show answer and solution

Correct option: B

Solution

Since A ⊂ B, we have P(A|B) = P(A∩B)/P(B) = P(A)/P(B). Because P(B) ≤ 1, dividing P(A) by P(B) gives P(A)/P(B) ≥ P(A). Hence P(A|B) ≥ P(A) always holds.

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