SFF wrote:
A 5-digit code consists of one number digit chosen from 1, 2, 3 and four letters chosen from A, B, C, D, E. If the first and last digit must be a letter digit and each digit can appear more than once in a code, how many different codes are possible?
A. 375
B. 625
C. 1,875
D. 3,750
E. 5,625
Let’s determine the number of ways we can produce each digit.
If L denotes a letter digit and N denotes a number digit, the possibilities for the code are L-N-L-L-L, L-L-N-L-L, and L-L-L-N-L. Note that
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