Probability

2009-12-05 2:09 am
One letter is chosen from each of the 3 words SHOE, SHY and SHUT. Find the probability that only 2 of the 3 letters are identical.

回答 (1)

2009-12-05 2:51 am
✔ 最佳答案
P(only 2 of the 3 letters are identical)

= P(S + S + H/U/T) + P(S + H/Y + S) + P(H/O/E + S + S)

+ P(H + H + S/U/T) + P(H + S/Y + H) + P(S/O/E + H + H)

= [ (1/4)(1/3)(3/4) + (1/4)(2/3)(1/4) + (3/4)(1/3)(1/4) ] * 2

= (1/16 + 1/24 + 1/16) * 2

= 1/3


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