1) As of April 2006, approximately 50 million web.com domain names were registered (eg, yahoo.com). a) How many domain names composed of exactly two letters can be formed? How many two-letter domain names are there if digits and numbers are allowed as characters? [Note: A character length of three or more is now required.] b) How many domain names are there composed of three letters? How many of this length are there if letters or digits are allowed? [Note: Currently all are used.
counting techniques and probability - Statistics and probability
1) As of April 2006, approximately 50 million web.com domain names were registered (eg, yahoo.com).
a) How many domain names composed of exactly two letters can be formed? How many two-letter domain names are there if digits and numbers are allowed as characters? [Note: A character length of three or more is now required.]
b) How many domain names are there composed of three letters? How many of this length are there if letters or digits are allowed? [Note: Currently all are used.]
c) As of April 2006, 97,786 of the four-character sequences using letters and digits had not yet been claimed. If a four-character name is chosen at random, what is the probability that it already has an owner?
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