AB
+BA
___
121
In the addition problem above, A and B represent digits in two different two-digit numbers. What is the sum of A and B?  Choose the most appropriate option.
A) 6
B) 8
C) 9
D) 11
E) 14
two ways to do it..   1) straight logic..   we can see that ones digit is 1 when units digit B and A are added..   answer has to be 1 in the units digit..   only 11 fits in..   2) BA=10B+A, and   AB=10A+B..   it is given that BA+AB=121..   or 10B+A +10A+B=121..   11(A+B)=121..   so A+B=11..   ANSWER:11
<result>D</result>
AB
+BA
___
121
In the addition problem above, A and B represent digits in two different two-digit numbers. What is the sum of A and B?