2

Part of 1997 Spain Mathematical Olympiad

Problems(1)

max No. 3 of 16 vertices on 4x4 grid, do not form an isosceles right triangle

Source: Spanish Mathematical Olympiad 1997 P2

A square of side

5

is divided into

25

unit squares. Let

A

be the set of the

16

interior points of the initial square which are vertices of the unit squares. What is the largest number of points of

A

no three of which form an isosceles right triangle?

combinatoricsgridSquaressquare gridmaximum