The positive two-digit integers a and b have the same digits, but in reverse order. Which of the following must be a factor of a + b?	Select.
A) 6 B) 9 C) 10 D) 55 E) 14
Remember: When you take the difference between the two, it will always be 9. e.g 23-32=9, 89-98=9   and when you add both integers, the sum will always be a multiple of 11 e.g 23+32=55, 89+98= 187   55 is multiple of 11   So, Answer 55
<result>D</result>
The positive two-digit integers a and b have the same digits, but in reverse order. Which of the following must be a factor of a + b?