WAEC 2020 · Paper 1 · Q40

A box contains 12 identical balls of which 5 are red, 4 blue and the rest green. If two balls are selected at random one after the other with replacement, what is the probability that both are red?

Worked solution (try it first)
  1. Each pick is red with probability 512\frac{5}{12}.
  2. With replacement the picks are independent, so multiply: 512×512=25144\frac{5}{12} \times \frac{5}{12} = \frac{25}{144}, option A.

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