a) If 6n tickets numbered 1 ,1,0 ,2 K, 6n are placed in a bag and three are drawn out,

show that the probability that the sum of the numbers on them is equal to 6n is

3n /(6n 6()1 n )2 . (5)

b) From a bag containing 3 white and 5 black balls, 4 balls are transferred into an empty

vessel. From this vessel a ball is drawn and is found to be white. What is the

probability that out of four balls transferred 3 are white and 1 is black?