SOLUTION: How many possible security codes can be made using 4 digits followed by 3 letters if (a) digits and letters can be repeated and (b) digits and letters can not be repeated?

Question 619063: How many possible security codes can be made using 4 digits followed by 3 letters if (a) digits and letters can be repeated and (b) digits and letters can not be repeated?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
How many possible security codes can be made using 4 digits followed by 3 letters if
(a) digits and letters can be repeated
10*10*10*10*26*26*26 = 175,760,000
.
(b) digits and letters can not be repeated?
10*9*8*7*26*25*24 = 78,624,000
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