Question 1138074: An identification code is to consist of 4 letters followed by 3 digits. Determine the following.
a) How many different codes are possible if repetition of letters is permitted, repetition of numbers is not permitted, and the first three entries must all be the same letter?
b) How many different codes are possible if the first letter must be an A, B, C, or D and repetition is not permitted?
Answer by VFBundy(438)   (Show Source):
You can put this solution on YOUR website! a) How many different codes are possible if repetition of letters is permitted, repetition of numbers is not permitted, and the first three entries must all be the same letter?
26 * 1 * 1 * 26 * 10 * 9 * 8 = 486,720
b) How many different codes are possible if the first letter must be an A, B, C, or D and repetition is not permitted?
4 * 3 * 2 * 1 * 10 * 9 * 8 = 17,280
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