MathDB

1

Part of 2023 Iberoamerican

Problems(1)

Finding Agent 7 in Brazil

Source: IberoAmerican 2023, Day 1, P1

9/8/2023
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.
number theory