試題詳解

23. (5%) Recently, Larry taught his daughter Emily how to play a game. To encourage Emily to practice this game, Larry decides to play with her until she wins two of the recent three games. Assume that either of the two players wins and the game cannot have a tie. If the probability that Emily a game is 1/4 independently of all preceding and future games, find the expected number of games to be played. 
(A) 121/9 
(B) 130/11
(C) 203/16
(D)89/7
(E) 55/4