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UI Post-UTME Mathematics 2025 (Model questions) Question 8

Question 8

Probability

A bag contains 5 red balls, 4 blue balls and 3 green balls. Two balls are drawn successively without replacement. What is the probability that the two balls are of different colours?

  1. A.7/11
  2. B.35/66
  3. C.47/66
  4. D.19/33
Show the answer and explanation

Answer: C (47/66)

Explanation

P(same colour) = (5×4 + 4×3 + 3×2)/(12×11) = 38/132 = 19/66, so P(different) = 1 − 19/66 = 47/66.