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MathNet 2022-part-02 — 197 problems (EN–VI) Question 132

Math Olympiad Vault · MathNet 2022-part-02 — 197 problems (EN–VI)

Question 132

For a fixed positive integer $k$, let $K$ be the set of all lattice points $(x, y)$ in the plane whose two coordinates $x$ and $y$ are both nonnegative integers less than $2k$. Thus $|K| = 4k^{2}$.

Now let $V$ be a set of $k^{2}$ non-degenerate quadrilaterals with the following properties:

i) The vertices of all these quadrilaterals are elements of $K$.

ii) Every point of $K$ is a vertex of exactly one of the quadrilaterals in $V$.

Determine the largest possible value of the sum of the areas of all $k^{2}$ quadrilaterals in $V$.