Four balls are drawn at random from a bag containing 5 white, 4 green and 3 black balls. The probability that exactly two of them are white is:

Total number of balls = 12 Hence, required probability = =5C2×7C212C4=1433 ∵ no of ways of drawing 2 white balls from 5 white balls = 5C2 .Also, no of ways of drawing 2 other from remaining 7 balls = 7C2