An Internet service provider requires its customer to select a password consisting of four letters followed by three digits. Find how many such passwords are possible in each of the following cases:
|(a)||Repetition of letters and digits is allowed.|
|(b)||Repetition of letters and digits is not allowed.|
The number of passwords which can be created when repetition of letters and digits is allowed.
The Fundamental counting principle states that “For any number of events occurs in number of ways, then the whole event can occur in ways.”
The number of ways in which the password can be created is given by,
The password has first four units as letters and the next three units as digits. Repetition is of letters and digits are allowed.
Number of letters are and number of digits are
The number of passwords which can be created when repetitions of letters and digits is not allowed.
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