Question 65
Calculate the sum $$
1+11+111+1111+\cdots+\underbrace{1111 \ldots 11}_{n \text{ some }}
$$
1+11+111+1111+\cdots+\underbrace{1111 \ldots 11}_{n \text{ some }}
$$
MathNet 2026 — Part 02 Question 65
Math Olympiad Vault · MathNet 2026 — Part 02