Problem:
The addition below is incorrect. The display can be made correct by changing one digit , wherever it occurs, to another digit . Find the sum of and .
Answer Choices:
A.
B.
C.
D.
E. more than
Solution:
The addition in the columns containing the ten-thousands and hundred-thousands digits is incorrect. The only digit common to both these columns is . Changing these 's to 's makes the arithmetic correct. Changing the other two 's to 's has no effect on the correctness of the remainder of the addition, and no digit other than could be changed to make the addition correct. Thus, , and .