A box contains 5 red, 3 green and 4 blue balls. A boy is allowed to take away two balls from the box. What is the probability that one is green and the other is blue?

  • A \(\frac{2}{11}\)
  • B \(\frac{5}{12}\)
  • C \(\frac{8}{12}\)
  • D \(\frac{7}{11}\)
waec 2001mathematics

The correct answer is A. \(\frac{2}{11}\)

Total number of balls = 5 + 3 + 4 = 12 balls

P(one ball is green and the other is blue) = P(first ball is green and second blue) + P(first ball is blue and the second green)

 = \(\frac{3}{12} \times \frac{4}{11} + \frac{4}{12} \times \frac{3}{11}\)

= \(\frac{2}{11}\)

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