SOLUTION: 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 ​permitt

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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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