Two cards are drawn from a pack and kept out. Then one card is drawn from remaining 50 cards.Find the prob. that it is an ace.

There are three cases for first two cards be drawn:

(i) two cards drawn are aces:

Probability in this case = Probability of getting 2 aces * Probability of getting third card to be an ace

(ii) one isace, one is not:

Probability in second case =

(iii) none of them is ace:

Probability in third case =

As, all the three cases are mutually exclusive , therefore by using addition theorem,