The probabilities that Ade, Kujo and Fati will pass an examination are \(\frac{2}{3}, \frac{5}{8}\) and...

MATHEMATICS
WAEC 2002

The probabilities that Ade, Kujo and Fati will pass an examination are \(\frac{2}{3}, \frac{5}{8}\) and \(\frac{3}{4}\) respectively. Find the probability that

(a) the three ;

(b) none of them ;

(c) Ade and Kujo only ; will pass the examination.

Explanation

(a) \(P(Ade) = \frac{2}{3} ; P(Kujo) = \frac{5}{8} ; P(Fati) = \frac{3}{4}\)

\(P(\text{all three pass the exam}) = \frac{2}{3} \times \frac{5}{8} \times \frac{3}{4}\)

= \(\frac{5}{16}\)

(b) P(Ade fails) = \(1 - \frac{2}{3} = \frac{1}{3}\)

P(Kujo fails) = \(1 - \frac{5}{8} = \frac{3}{8}\)

P(Fati fails) = \(1 - \frac{3}{4} = \frac{1}{4}\)

P(none passes) = \(\frac{1}{3} \times \frac{3}{8} \times \frac{1}{4}\)

= \(\frac{1}{32}\).

(c) P(Ade and Kujo only pass) = \(\frac{2}{3} \times \frac{5}{8} \times \frac{1}{4}\)

= \(\frac{5}{48}\)



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