急 ! F5 數 Probability 1條 5q9

25. (iii)
The required probability
= P(first turn white sock) x P(second turn white sock) x (third turn blacksock)
= (6/10) x (5/9) x (4/8)
= 3/18


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35.
(a)(i)
At least number of turns = 3
(One team gets 3 scores, and another term gets 0 scores. The latterwould gets at most 2 scores in the last two turns.)

(a)(ii)
The required probability
= P(AXXX, B√√√)
= (1 - 0.88) x (1 - 0.83) x (1 - 0.72) x 0.90 x 0.88 x 0.79
= 0.00357

(b)
Consider the last two turns only.
The required probability
= [P(A√√, B√X) + P(A√√, BX√)] + [P(A√√, BXX) + P(A√X, BXX) + P(AX√, BXX)]
= 0.60x0.91x[0.58x(1-0.62) + (1-0.58)x0.62] + [0.60x0.91 + 0.60x(1-0.91) +(1-0.60)x0.91]x(1-0.58)x(1-0.62)
= 0.416