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JAMB Mathematics 2000 Question 41

Question 41

Probability

X and Y are two events. The probability of X or Y is 0.7 and the probability of X is 0.4. If X and Y are independent, find the probability of Y.

  1. A.0.30
  2. B.0.50
  3. C.0.57
  4. D.1.80
Show the answer and explanation

Answer: B (0.50)

Explanation

For independent events, P(X or Y) = P(X) + P(Y) − P(X)P(Y). So 0.7 = 0.4 + y − 0.4y, giving 0.6y = 0.3 and y = 0.5.