Question 1
What is the smallest possible number of different leading decimal digits among $n,2n,3n,\ldots,9n$, where $n$ is a positive integer? (5 points)
Neutral editorial illustration.
Practice scoring adds all whole-question scores (maximum 57). Official ITOT scoring adds only the three highest whole-question scores (maximum 28), after summing subparts within each question. The importer does not enforce best-three scoring. Duration: 300 minutes from historical organizer general rules, not an individually printed duration on this paper.
Neutral editorial illustration.
Practice scoring adds all whole-question scores (maximum 57). Official ITOT scoring adds only the three highest whole-question scores (maximum 28), after summing subparts within each question. The importer does not enforce best-three scoring. Duration: 300 minutes from historical organizer general rules, not an individually printed duration on this paper.