Question 1125693: Students log on to the California Virtual Campus with a user name consisting of 8 characters: 4 uppercase letters of the alphabet followed by 4 digits. How many user names begin with A and end with 9?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! Assume a letter/number may be used more than once.
For the second, there are 26 choices and same for third and fourth, 26*26*26
Then there are 10*10*10 ways to choose the next three digits.
17,576,000 possibilities.
Note: the first letter has already been chosen, and there are only three more left, each of which has 26 possibilities. The last number has been chosen, and there are only three left, each of which has 10 possibilities, 0,1,2,3,4,5,6,7,8 and 9.
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