Question 220: A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?
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Total number of balls = (2 + 3 + 2) = 7.Let S be the sample space.Then,n(S)= Number of ways of drawing 2 balls out of 7=7C2`=(7 x 6)(2 x 1)= 21.Let E = Event of drawing 2 balls, none of which is blue.n(E)= Number of ways of drawing 2 balls out of (2 + 3) balls.=5C2=(5 x 4)(2 x 1)= 10.P(E) =n(E)=10.n(S)21