Question
A bag contains 6 purple balls, 9 yellow balls and 5
green balls. Three balls are drawn at random. Find the probability that at least two balls are yellow.Solution
Total = 6 + 9 + 5 = 20
Required probability = (Two yellow and one other) + (Three yellow)
= 3 × [(9/20) × (8/19) × (11/18)] + (9/20 × 8/19 × 7/18)
= (2376/6840) + (504/6840)
= (2880/6840) = (24/57) = 8/19
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