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JAMB Mathematics 2006 Question 5

Question 5

Probability

A bag contains 5 black, 4 white and x red marbles. If the probability of picking a red marble is 2/5, find the value of x.

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

Answer: D (6)

Explanation

x/(9 + x) = 2/5 gives 5x = 18 + 2x, so x = 6.