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JAMB Mathematics 1995 Question 49

Question 49

Probability

Let P be a probability function on set S, where S = {a1, a2, a3, a4}. Find P{a1} if P{a2} = ⅓, P(a3) = ⅙ and P(a4) = ⅕.

  1. A.7/10
  2. B.⅔
  3. C.⅓
  4. D.3/10
Show the answer and explanation

Answer: D (3/10)

Explanation

The four probabilities must add up to 1. P(a₁) = 1 − (⅓ + ⅙ + ⅕) = 1 − 21/30 = 9/30 = 3/10.