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I know mentioned it before, but I really appreciate providing any way of solving the problem. I really need to solve the problem.. please help!

Thanks in advance for you thoughts shared.

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- Thread starter Cylab
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- #1

- 54

- 0

I know mentioned it before, but I really appreciate providing any way of solving the problem. I really need to solve the problem.. please help!

Thanks in advance for you thoughts shared.

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- #2

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Start wit the simplest case. What is the probability of guessing

- #3

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Analysis:

1st, Sample space: there are 26 letters and each of them can be filled up and thus sample space is 26*26*26*26*26=26^5.

2nd, let`s restrict that first letter (FL) must be one of 'A~V' (the order of 5 correct letters is same as the order of 'A~Z'), thus P(FL)=1/21. Second letter(SL) would be, if FL is 'A', is one of 'B~W', thus P(SL)=1/21 as well. But if FL is 'C', SL is one of 'C~W', thus P(SL)=1/20 . Once FL is 'D','E','F'... , then P(SL)=1/19,1/18,1/17 respectively...Thus, P(SL)=1/21+1/20... Third Letter is...This is long calculation, but I was wondering if there is any alternative way doing that...

Please feel free to offer your suggentions.

Thanks again for sharing ideas!

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