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WAEC Further Mathematics 2014 Question 11

Question 11

Probability

A box contains 5 red and k blue balls. A ball is selected at random from the box. If the probability of selecting a blue ball is 2/3, find the value of k.

  1. A.5
  2. B.6
  3. C.8
  4. D.10
Show the answer and explanation

Answer: D (10)

Explanation

k/(5 + k) = 2/3 gives 3k = 10 + 2k, so k = 10.