Problem:
Let A,M, and C be nonnegative integers such that A+M+C=10. What is the maximum value of Aβ
Mβ
C+Aβ
M+Mβ
C+Cβ
A?
Answer Choices:
A. 49
B. 59
C. 69
D. 79
E. 89
Solution:
Note that
AMC+AM+MC+CA=(A+1)(M+1)(C+1)β(A+M+C)β1=pqrβ11,
where p,q, and r are positive integers whose sum is 13. A case-by-case analysis shows that pqt is largest when two of the numbers p,q,r are 4 and the third is 5. Thus the answer is 4β
4β
5β11=69.
Answer: Cβ.
The problems on this page are the property of the MAA's American Mathematics Competitions