ISL 2017 N4
- Answer
Call a rational number short if it has finitely many digits in its decimal expansion. For a positive integer , we say that a positive integer is -tastic if there exists a number such that is short, and such that is not short for any . Let be the set of -tastic numbers. Consider for . What is the maximum number of elements in ? (Turkey)
Dataset text NuminaMath olympiads. Quoted with source.
Official text: IMO 2017 Shortlist booklet, page 12.
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Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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