A local bank that has 18 branches uses a two-digit code to represent each of its branches. The same integer can be used for both digits of a code, and a pair of two-digit numbers that are the reverse of each other (such as 17 and 71) are considered as two separate codes. What is the fewest number of different integers required for the 18 codes? Pick
A) 3  B) 4  C) 5  D) 6  E) 18( 5 integers 25 codes
Pick any two integer.   Integers: 12   Code: 11, 12, 21, 22 = 4 Codes   Add one more integer: 3   13, 31, 33, 23, 32 = 5 Codes   Add one more integer: 4   44, 14, 41, 24, 42, 34, 43 = 7 Codes   Add one more integer: 5   55, 15,51, 25,52,35,53,45,54 =9 codes   Total = 25 Codes. Enough. Answer: E   5 integers create 25 codes.   18( 5 integers 25 codes
<result>E</result>
A local bank that has 18 branches uses a two-digit code to represent each of its branches. The same integer can be used for both digits of a code, and a pair of two-digit numbers that are the reverse of each other (such as 17 and 71) are considered as two separate codes. What is the fewest number of different integers required for the 18 codes?