Problem:
The digit-sum of is . How many -digit whole numbers, whose digit-sum is , are even?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
The only -digit whole numbers with a digit-sum of are and . Of these, only is even. Thus there is only one such number.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions