The probability of an event P happening is \(\frac{1}{5}\) and that of event Q is...

MATHEMATICS
WAEC 2014

The probability of an event P happening is \(\frac{1}{5}\) and that of event Q is \(\frac{1}{4}\). If the events are independent, what is the probability that neither of them happens?

  • A. \(\frac{4}{5}\)
  • B. \(\frac{3}{4}\)
  • C. \(\frac{3}{5}\)
  • D. \(\frac{1}{20}\)

Correct Answer: C. \(\frac{3}{5}\)

Explanation

prob(p) = \(\frac{1}{5}\)

prob(Q) = \(\frac{1}{4}\)

Prob(neither p) = 1 - \(\frac{1}{5}\)

\(\frac{5 - 1}{5} = \frac{4}{5}\)

prob(neither Q) = 1 - \(\frac{1}{4}\)

\(\frac{4 - 1}{4} = \frac{3}{4}\)

prob(neither of them) = \(\frac{4}{5} \times \frac{3}{4} = \frac{12}{20}\)

= \(\frac{3}{5}\)



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