How many four-digit personal identification numbers (pin) are possible if the pin cannot begin with a 0 and the pin must be an odd number? a. 5,000 b. 4,500 c. 3,600 d. 500

Consider 4 positions of four-digit PIN:

1. PIN cannot begin with 0, then it can begin with 9 remaining digits (1, 2, 3, 4, 5, 6, 7, 8 and 9) - 9 posibilities;

2. for the second and third position yuo can select any of 10 digits (0, 1, 2, 3, 4, 5, 6, 7, 8 and 9) - 10·10=100 posibilities;

3. the PIN must be an odd number, then it ends with any of 5 odd digits (1, 3, 5, 7 and 9) - 5 posibilities.

Use the product rule to count the total number of posibilities:

9·100·5=4500.

correct choice is B.

step-by-step explanation:

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