a,b and c are positive integers less than or equal to 9. If a,b and c are assembled into the six-digit number abcabc, which of the following must be a factor of abcabc? Choices
A) 7
B) 9
C) 11
D) 3
E) none of these
The sum of the digits in place 1,3 and 5 is a+c+b is equal to the sum of the digits in place 2,4 and 6 which is b+a+c. thus the number abcabc is divisible by 11. thus 11 must be a factor of abcabc.   Answer: 11
<result>C</result>
a,b and c are positive integers less than or equal to 9. If a,b and c are assembled into the six-digit number abcabc, which of the following must be a factor of abcabc?