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MathNet 2000 — Math Olympiad Vault Question 151

Math Olympiad Vault · MathNet 2000 — Math Olympiad Vault

Question 151

Let
$$S=\frac1n+\frac1{n+1}+\cdots+\frac1{n+m},\qquad n,m\in\{1,2,3,\ldots\}.$$
a) Prove that $S$ cannot be a natural number.

b) For $m=2(n-1)$, find, with justification, $k\in\mathbb N$ such that $k\lt S\lt k+1$.