From a bag containing 4 white and 5 red balls, if 3 balls are drawn at random, then the mean of the number of red balls among the balls drawn, is

Step-by-step solution

Let the random variable is (X ), then ( array ccccc x & 0 & 1 & 2 & 3 P(X) & ^4 C₃ ^9 C₃ & ^4 C₂ ^5 C₁ ^9 C₃ & ^4 C₁ ^5 C₂ ^9 C₃ & ^4 C₀ ^5 C₃ ^9 C₃ array ) ( aligned Mean = & 0 ( ^4 C₃ ^9 C₃ )+1 ( ^4 C₂ ^5 C₁ ^9 C₃ ) & +2 ( ^4 C₁ ^5 C₂ ^9 C₃ )+3 ( ^4 C₀ ^5 C₃ ^9 C₃ ) & = (6 5)+(2 4 10)+(3 10) 9 8 7 3 2 = & 30+80+30 84 = 140 84 = 5 3 aligned ) Hence, option (a) is correct.