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MathNet 2022-part-01 — 197 problems (EN–VI) Question 30

Math Olympiad Vault · MathNet 2022-part-01 — 197 problems (EN–VI)

Question 30

Find all positive integers $k\lt 202$ for which there exists a positive integer $n$ such that
$$
\left\{\frac{n}{202}\right\}+\left\{\frac{2 n}{202}\right\}+\cdots+\left\{\frac{k n}{202}\right\}=\frac{k}{2}
$$
where $\{x\}$ denote the fractional part of $x$.
Note: $\{x\}$ denotes the real number $k$ with $0 \leq k\lt 1$ such that $x-k$ is an integer.