Case 1: All three balls selected are of the same colour. The balls selected could be all blue, all white or all black. H ence there are 3 possible colours for selection. Number of ways = 3C1 Case 2: Exactly two balls selected are of the same colour. The two same coloured balls selected could either be both red, both blue, both white or both black. Hence 4 possible colours for selection give 4C1 ways. The third ball selected could of any of the remainingthree colours and hence can be selected in 3C1 ways. Number of ways =3C1.4C1 Total ways = 3C1+3C1.4C1