Posted by manny on .
Suppose a code consist of two letters followed by a digit. Find the number of
(a) Codes
(b) Codes with distinct letters
(c) Codes with the same letters

math 
mathstudent,
Assuming there are 26 letters (no distinction among case) and 10 digits:
A) 26 * 26 * 10 = 6760
B) 26 * 25 * 10 = 6500
C) 26 * 1 * 10 = 260 
math 
Anonymous,
a) Codes
The way of labeling a code with two letters followed by a digit
Assigning one of the 26 letters: A, B, C, D…., F
Assigning one of the 10 digits: 0, 1, 2…, 9
There are two letters so 26
By product rule there are 26×26×10 = 6760 codes
b) Codes with distinct letters
The way the distinct letters are label
25 character of first letters and 25 characters for the second letter so
There are 26×25×10=6500 codes
c) Codes with same letters
The way the same letters are label
26×1×10=260 codes