The diagram below shows the keypad for an automatic teller machine. As you can see, the
Chapter 9, Problem 18(choose chapter or problem)
The diagram below shows the keypad for an automatic teller machine. As you can see, the same sequence of keys represents a variety of different PINs. For instance, 2133, AZDE, and BQ3F are all keyed in exactly the same way.
a. How many different PINs are represented by the same sequence of keys as 2133?
b. How many different PINs are represented by the same sequence of keys as 5031?
c. At an automatic teller machine, each PIN corresponds to a four-digit numeric sequence. For instance, TWJM corresponds to 8956. How many such numeric sequences contain no repeated digit?
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