Question
A box contains 4 red, 5 blue and 3 green balls. Two
balls are drawn at random without replacement. Find the probability that both balls are of the same colour.Solution
Total balls = 4 + 5 + 3 = 12 Total ways to choose 2 balls = 12C2 = 66 Favourable cases (same colour): Red: 4C2 = 6 Blue: 5C2 = 10 Green: 3C2 = 3 Total favourable = 6 + 10 + 3 = 19 Required probability = 19/66.
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