Alisa T.

asked • 08/01/22

How many five letter words have at least a pair of the same letters?

Mark M.

Are these only English words? Or can they be any words? Must the words make sense? Question too vauge!
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08/01/22

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Yefim S. answered • 08/01/22

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P(at least 2 the same) = 1 - P(26,5)/265 = 1 - 26·25·24·23·22/265 = 0.3356325059

So, number n of such a words: n = 265 - 26·25·24·23·22 = 3987776

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David W.

Not Probability. "How many 5-letter sequences can be made from 26 letters such that each sequence has at least two of the same letter?"
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08/01/22

Mark M.

David W.: Yet how many five letter sequences are five letter words. The problem is poorly stated.
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08/01/22

David W.

After re-wording, this is indeed the "Birthday Problem". There are 3,987,776 such 5-letter sequences.
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08/02/22

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