MathDB
Finding Agent 7 in Brazil

Source: IberoAmerican 2023, Day 1, P1

September 8, 2023
number theory

Problem Statement

Let nn be a positive integer. The following 3535 multiplication are performed: 1⋅n,2⋅n,…,35⋅n.1 \cdot n, 2 \cdot n, \dots, 35 \cdot n. Show that in at least one of these results the digit 77 appears at least once.
Back to ProblemsView on AoPS