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MathNet 2017-part-01 — 176 problems (EN–VI) Question 113

Math Olympiad Vault · MathNet 2017-part-01 — 176 problems (EN–VI)

Question 113

Consider the following grid board in which all natural numbers were written diagonally.

| $\ddots$ | | | | | |
| :---: | :---: | :---: | :---: | :---: | :---: |
| 10 | $\ddots$ | | | | |
| 6 | 9 | $\ddots$ | | | |
| 3 | 5 | 8 | 12 | $\ddots$ | |
| 1 | 2 | 4 | 7 | 11 | $\ddots$ |

Each small square has a position denoted by $(x, y)$, where $x$ is the column, counted from left to right, and $y$ is the row, counted from bottom to top. For example, 12 is the number written in the square at position $(4,2)$:

a) Determine the number in the square at position $(4,4)$.

b) Determine the number in the square at position $(1,2016)$.

c) Determine the number in the square at position $(2013,2017)$.