Problem:
The numbers from to are arranged in a spiral pattern on a square grid, beginning at the center. The first few numbers have been entered into the grid below. Consider the four numbers that will appear in the shaded squares, on the same diagonal as the number . How many of these four numbers are prime?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
We can fill in the other numbers to get the complete grid.
From this, we can see that the only prime numbers in the shaded boxes are and . Thus, is the correct answer.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions