Question

Suppose a certain web site has you choose a username and a
password where the username consists of 9 alphanumeric characters
and the password is 6 alphanumeric characters the last of which
must be numeric and the first of which must be alphabetical.

a. How many usernames are possible if they are not case
sensitive?

b. How many passwords are possible if they are not case
sensitive?

c. How many usernames are possible if they are case sensitive?

d. How many passwords are possible if they are case sensitive?

Answer #2

Number of alphabetical characters = 26

Number of numerical characters = 10

Number of alphanumeric character options if not case sensitive = 26 + 10 = 36

Number of alphanumeric character options if case sensitive = 26x2 + 10 = 62

a. Number of usernames possible, not case sensitive =
36^{9}

= **1.016x10 ^{14}**

b. Number of passwords possible, not case sensitive = 26 x
36^{4} x 10

= **4.367x10 ^{8}**

c. Number of usernames possible, case sensitive =
62^{9}

= **1.354x10 ^{16}**

b. Number of passwords possible, case sensitive = 52 x
62^{4} x 10

= **7.684x10 ^{9}**

answered by: anonymous

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