Problem:
Placing no more than one in each small square, what is the greatest number of 's that can be put on the grid shown without getting three 's in a row vertically, horizontally, or diagonally?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
The arrangement pictured shows 's is possible. If there were 's on a board, then one row must contain 's.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions