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A box contain 2 white and 3 blue identical balls. If two balls are picked...

Mathematics
WAEC 1998

A box contain 2 white and 3 blue identical balls. If two balls are picked at random, one after the other, without replacement, what is the probability of picking two balls of different colours?

  • A. \(\frac{5}{25}\)
  • B. \(\frac{7}{20}\)
  • C. \(\frac{3}{5}\)
  • D. \(\frac{2}{3}\)
  • E. \(\frac{5}{6}\)
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Correct Answer: Option C
Explanation

Balls were picked without replacement

n( white balls) = 2,  n( black balls ) = 3 

Total Balls = 2 + 3 = 5 balls

Pr( two balls of different colours ) = WB OR BW

                                                = \(\frac{2}{5} \times \frac{3}{4} + \frac{3}{5} \times \frac{2}{4}\)

                                                  =  \(\frac{6}{20} + \frac{6}{20}\) = \(\frac{12}{20}\) = \(\frac{3}{5}\)

 


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