1.

A box contains 5 red, 4 black and 4 blue balls. If 3 balls are drawn randomly from the box, what is the probability that there are exactly 2 blue balls in the three drawn balls ?

Answer»

27/143



Total BALLS = 5 + 4 + 4 = 13
∴ n(S) = 13C3 = 286
2 blue balls can be selected from 4 balls in 4C2 = 6 ways and the REMAINING one BALL is to be selected from 9 balls in 9C1 = 9 ways 
∴ n(E) = 6 x 9
∴ P(E) = 6 x 9/286 = 27/143



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